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HX64122182 
RC78  .H61  The  principles  and  p 


RECAP 


rmcipies  and  Practice 


1 

! 

I  Setli  Hirsc 


f^GT^ 


Columbia  ?lSnibers;itp  (LooA 


3^ef  erence  Mjrarp 


/ 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


/http://www.archive.org/details/principlespractiOOhirs 


THE  PRINCIPLES  AND   PRACTICE 

OF 
ROENTGENOLOGICAL  TECHNIQUE 


The  Principles  and  Practice 

of 

Roentgenological  Technique 


By 
I.  SETH  HIRSCH,  M.  D. 

Director  X-Ray  Departments 

Bellevue,  Fordham,  Harlem  and  Gouvemeur  Hospitals 

New  York  City 


With  Three  Hundred  and  Forty-three  Illustrations 
and  Twenty-two  Tables 


American  X-Ray  Publishing  Co. 

New  York 

1920 


Copyright  1919 
American  X-Ray  Publishing  Co. 


0  -  -I.  5"   -7 


A 


TO  MY  MOTHER 


PREFACE 


"  I  said  that  in  writing  it  took  more  time  and  trouble  to  get  a 
thing  short  than  long.  It  was  harder  not  to  paint  a  detail  than  to 
paint  it,  easier  to  put  in  all  that  one  can  see  than  to  judge  what  may 
go  without  saying,  omit  it  and  range  the  irreducible  minima  in  due 
order  of  precedence.     Hence  we  all  lean  towards  prolixity. 

"  The  difficulty  lies  in  the  nice  appreciation  of  relative  impor- 
tances and  in  the  giving  each  detail  neither  more  nor  less  than  its  due. 

"  Bearing  in  mind  the  shortness  of  life  and  the  comple.xity  of 
affairs,  it  stands  to  reason  that  we  owe  most  to  him  who  packs  our 
trunks  for  us,  so  to  speak,  most  intelligently,  neither  omitting  what 
we  are  likely  to  want,  nor  including  what  we  can  dispense  with,  and 
who,  at  the  same  time,  arranges  things  so  that  they  will  travel  most 
safely  and  be  got  at  most  conveniently." 

Samuel  Butler. 


What  the  author  has  earnestly  striven  to  do  is  to  pack  the  kit  of  the  student 
of  Roentgenology  with  those  principles  of  technique  which  will  serve  him  best 
on  the  difficult  road  to  the  goal — Roentgenological  diagnosis  and  therapy. 

In  this  aim  he  has  been  guided  by  an  experience  in  teaching  extending  over 
many  years.  The  fundamental  facts  and  theories  relating  to  electricity  and  its 
application  to  the  construction  of  the  apparatus  in  use  in  a  Roentgenological 
laboratory  have  been  outlined  in  as  concise  and  practical  a  form  as  possible. 
A  clear  comprehension  of  these  principles  is  necessary  for  the  correct  use  of 
such  instruments. 

In  his  discussion  of  the  technical  methods,  the  author  has  sought  to  follow 
the  ordinary  sequence  of  activities  involved  in  the  making  of  a  Roentgenological 
examination,  omitting  such  theoretical  considerations  as  have  no  direct  practical 
bearing  on  the  problem. 

It  is  impossible  for  the  author  to  render  full  acknowledgment  to  all  the 
sources  which  have  aided  him  in  the  preparation  of  this  volume.  The  clearest 
thought  and  its  most  lucid  expression  have  been  gathered  wherever  available  and 
presented  in  the  form  which  practical  experience  has  shown  will  most  forcibly 
impress  the  student  mind. 

He  has  received  much  inspiration  from  many  illuminating  articles  in  the 
American  Journal  of  Roentgenology  and  the  Archives  of  Electro-Therapeutics 
and  Radiology,  by  W.  D.  Coolidge,  J.  S.  Shearer  and  others,  and  has  derived 
much  aid  from  standard  textbooks  in  all  languages. 

To  Mr.  Morse  Sable  Hirsch  the  author  extends  his  thanks  for  many  invalu- 
able suggestions  and  constructive  criticisms. 

Grateful  acknowledgment  is  rendered  to  Dr.  Frank  Wheatley  and  W.  W. 
Mowry  for  their  capable  and  unselfish  aid  and  their  services  in  reading  proof, 
to  W.   M.   Morison   for   many   photographs   and   to   his   associates   at   Bellevue 

Hospital  for  their  cooperation. 

I.  Seth  Hirsch. 
11  East  68th  Street, 
New  York  City. 


CONTENTS 

PART  I.  PART  II. 

PRINCIPLES   OF  TECHNIQUE  THE    APPLICATION    OF    THE    PRINCIPLES 

OF  ROENTGENOLOGICAL  TECHNIQUE 
CHAPTER  L 

PACE  CHAPTER  NIL 

Principles   of   Electricitj' I  page 

Fluoroscopy   113- 

CHAPTER   II.  ^ 

Induction     Apparatus  —  Open      Core  —  Coil —  CHAPTER  NIII. 

Interrupters    23      Radiography 121 

CHAPTER  III.  CHAPTER  NIV. 

Induction  Apparatus  —  Closed  Core  —  Radiographic    Methods    131 

Interrupterless   34  CHAPTER  NV. 

CHAPTER  IV.  The  Silver  Bromide  Plate 137 

Portable    Induction   Apparatus 49  _      . 

CHAPTER  V.  Postures  and  Positions I39- 

The  Discovery  of  the  N-Ray 56  CHAPTER  NVIL 

CHAPTER  VI.  Standard  Positions   147 

The  Crookes'  or  Gas   Tubes 60  _^^  ,  ^^^„    ^-ttttt 

CHAPlER  A\  ill. 

CHAPTER  VII.  The  Exposure   I95 

The  Hot  Cathode  or  Electron  Tubes 68  ^^,  ,  „„„„  ,.Tt^ 

CHAP  ILR  AlN. 

CHAPTER  VIII.  Exposure  Tables    200 

The   Cathode   Discharge 75  CHAPTER  NN 

CHAPTER  IN.  The  Development  of  the  Plate 207 

The  X-Ray  and  its  Properties 77  \PTER  XXI 

CHAPTER  X.  The  Examination  of  the  Plate 213. 

The    Production    of    X-Rays 80  CHAPTER   XXII. 

CHAPTER  XL  The  X-Ray  Laboratory   217- 

The  Measurement  of   X-Rays 93      Index 235^ 


TABLES 

TABLE  PAGE 

I.    Wiring   Table    i8 

II.    Resistances   for  Fifteen   Ohms   Rheo- 
stat, 220  Volt  D.  C 41 

III.  Resistances    for    20    Ohms    Rheostat, 

220  Volt  A.  C 41 

IV.  Sparking   Potentials   93 

V.     Sphere-Gap    Spark   Voltages 94 

VI.     Point-Gap   Voltages    94 

VII.     Comparative    Values    of    Qualimeter 

Scales   g8 

VIII.     Comparative  Values  of  Various  Pene- 
trometer Units    99 

IX.    Absorption  Table  100 

X.     Depth   Dosages    100 

XI.     Table  of   Absorption   Quotients loi 

XII.     Filtration   and   Half-Absorption 102 

XIII.  Comparative   Radiometer   Values 106 

XIV.  Exposure  Values  as  Affected  by  Dis- 

tance   196 

XV.     Exposure     Values     as     Affected     by 

Thickness    ig8 

XVI.     Factorial     Values      (Thickness      and 

Density)   of  Parts  of  Body 200 

XVII.     Exposure   Seed   Plate    (Coolidge) 200 

XVIII.     Unit    Radiation    Table     for    Varying 

Depths    201 

XIX.     Exposure  Table  Based  on  a  Varying 
Penetration  according  to  Thickness 

of   Part    202 

XX.     Exposure  Table  Gas  Tube 204 

XXI.     Key  to  Above  Table 204 

XXII.     Exposure  Table  —  Coolidge  Tube....  205 


LIST  OF  ILLUSTRATIONS 


FIG. 
I. 
2. 


Sa. 
Sb. 
5C. 
Sd. 
56. 
5f- 


9- 

10. 

II. 

12. 

13- 

14. 

15- 
16. 

17- 
18. 

19- 
20. 
21. 
22. 

24- 

25- 
26. 
27. 
28. 
29. 
30. 

31- 
32. 
33- 
33a. 

34- 


Diagram    Illustrating   Ohm's    Law 

Plan   View   of   Field   of   Force   between 

Poles  of  a   Magnet 

Field  of  Force  between  Poles  of  a  Mag- 
net   (Profile   View) 

Diagram  of  Alternating  Generator 

Diagram  of  Direct  Current  Generator.. 

Cummutator  and  Brushes 

Diagram  Alternating  Current  —  25  Cycle 

Diagram   Oscillating  Current 

Diagram  Alternating  Current  —  60  Cycle 

Direct    Pulsating   Current 

Continuous    Direct    Current 

Direct   Constant   Current 

Diagram    Illustrating    Transmission    of 

Currents   

Diagram  of  A.  C.  Electro-Motive  Force 

—  Sine  Wave-form    

Current  Curve  of  Three-Phase  System. 
Current  Curves  of  Multiphase  System.. 

Scheme  of  Three  Wire   System 

Diagram   of   Simple   Converter 

Commutation   of   Alternating  Wave.... 
External  Circuit  of  Voltaic  Element.... 

Solenoid   in    Circuit 

Amperemeter    in    Circuit 

Shunt  in   Circuit 21 

Voltmeter    in    Circuit 21 

Soft    Iron    Amperemeter 21 

Moving   Coil  Voltmeter 22 

Moving   Coil   Voltmeter 22 

Ammeter    22 

\'oltmeter     22 

Faraday  Ring 23 

Plan  of   Construction  of   Coil 24 

Plan   of   Winding  of   Coil   and   Connec- 
tion to   Condenser  and   Break 26 

Mechanical    Break    27 

Jet  Type  Mercury  Interrupter 27 

Ring  Type  Mercury  Interrupter 28 

Cross  Section  of  Ring  Type  Break 20 

Electrolytic    Interrupter    29 

Multiple   Point  Wehnelt  Interrupter....       30 

Rheostat  31 

Diagram  of  Connections  of  Coil  Outfit.  32 
Closed  Magnetic  Circuit  Transformer. .  34 
Diagram       Illustrating      Principles      of 

Transformer   Action    35 

Construction     of      Closed-Core     Trans- 
former         35 


AGE 

FIG. 

6 

35- 

10 

36. 

27- 

II 

14 

38. 

14 

15 

Z9- 

16 

16 

40. 

16 

16 

41- 

16 

16 

42. 

16 

42a 

17 

43- 

17 

17 

44- 

17 

19 

19 

44a 

20 

44b 

20 

44c 

20 

45- 

46, 

47 


49. 
50. 
51 

52. 
53 
54 
55. 
56 


58 
59. 
60. 
61 
62, 
63 


P.AGE- 

Diagrammatic     Scheme     of     Rectifying 

Device   37 

Diagram  Showing  Reversal  of  Wave...  37 
Wiring      Diagram      of      Interrupterless 

Transformer,    D.    C 38- 

Wiring      Diagram      of      Interrupterless 

Transformer,  A.  C 39 

Wiring      Diagram      of      Interrupterless 

Transformer,   Disc   Commutation 40. 

Wiring     Diagram     Interrupterless     Ala- 
chine  and  Switchboard 40. 

Wiring    Diagram    A.    C.    Interrupterless 

Machine    4O) 

Auto-Transformer       Construction       and 

Connection  43: 

Diagram   Illustrating  Auto-Transformer 

Construction   and   Ratios 43^ 

Auto-Transformer    and    Rheostat    Con- 
trol       44; 

Transformer    Chart    of    Comparison    of 
Auto-Transformer       and       Rheostatic 

Control   44: 

Booster   Transformer    44 

Booster   Transformer    44, 

Booster   Transformer    45 

Wave  Forms  of  Primar\-  and  Secondary 

Currents   45 

Wave  Form  of  Transformer  Discharge  45 
Wave   Form    of   25   k.   w.    Transformer 

Discharge  45 

Oscilligram  of  a  Transformer  Discharge 

( Non-Commutated )     46 

Oscilligram  of  a  Coil  Discharge 46 

Converter  Unit  and  Control 47 

Converter  Unit  and  Control   (Parts  Ex- 
posed)      47 

Control   Panel  of   Converter  Unit 48 

Wiring  Diagram  of  Converter  Unit 48 

Portable  Coil  and  Storage  Batteries 49 

Gas  Engine  Generating  Set 50 

Wiring   Diagram   U.    S.   Army   Portable 

Unit   50 

Wiring   Diagram    U.    S.   Army    Bedside 

Unit  50 

U.  S.  Army  Portable  Unit 5i 

U.  S.  Army  Field  X-Ray  Outfit 51 

U.  S.  Army  Bedside  Unit 52 

Portable   Horizontal   Fluoroscopic  Table  52 

U.  S.  Army  X-Ray  Table 52> 

U.  S.  Army  X-Ray  Table 53 


XIV 


LIST  OF  ILLUSTRATIONS 


FIG.  PAGE 

64.  Mobile  X-Ray  Unit  —  French  Army....  53 

65.  Mobile  X-Ray  Unit  —  French  Army....  53 

66.  Mobile  X-Ray  Unit  —  French  Army....  53 
dj.       Wagon  Equipped  for  Field  X-Ray  Work  54 

67a.     Roentgen    Surgical   Aeroplane 5S 

67b.     Roentgen  Aeroplane  Unit 55 

67c.     Roentgen       Horizontal       Fluoroscope  — 

Aeroplane  Unit    55 

67d.     American  Roentgen-Ray  Camion 55 

68.       Crookes'    Experiment    57 

'69.       Lenard   Tube    57 

70.  Various  Forms  of  X-Ray  Tubes 60 

71.  Roentgen's   Experimental   Tube 60 

72.  Distribution     of     Electric     Charge     on 

X-Ray  Tube  61 

73.  Diagram  of  X-Ray  Tube 61 

74.  Double  Target   Stereoscopic  Tube 62 

75.  Water    Cooled    Tube 62 

76.  Oil    Cooled    Tube 63 

77.  Oil    Cooled    Tube 63 

78.  Oil    Cooled    Tube 64 

79.  Air-Cooled  Target  with  Radiator 64 

80.  Air-Regulating  Device    65 

81.  Hydrogen    Tube    65 

82.  Types  of  X-Ray  Tubes dj 

83.  Coolidge  Tube   68 

84.  Anode   of   Coolidge   Tube 68 

85.  Cathode  of  Coolidge  Tube 68 

86.  Step-Down      Transformer     and      Inter- 

rupter      69 

87.  Coolidge   Circuit    69 

88.  Coolidge    Circuit  —  Storage    Battery....  69 

89.  Connections      for      Coolidge      Filament 

Transformer  and  Control 70 

90.  Focal  Points  of  Various  Types  of  Cool- 

idge  Tubes    70 

91.  Fine    Focus     Coolidge    Tube,    Radiator 

Type 71 

92.  Lillienfeld  Tube  Circuit.. 72 

93.  Lillienfeld  Tube  Circuit 72 

94.  Lillienfeld   Tube    72 

■95.      Metal  Tube  73 

96.  Distribution   of   X-Rays 80 

97.  Photograph  Low  Vacuum  Tube 81 

98.  Photograph   Medium  Vacuum  Tube....  81 

99.  Photograph  Low  Vacuum  Tube 81 

■100.      Photograph  Low   Vacuum   Tube   Show- 
ing Cathode  Stream  81 

loi.       Photograph    Medium    Vacuum    Tube  — 

Fine  Focus    82 

102.  Photograph    Medium    Vacuum    Tube  — 

Broad   Focus    82 

103.  Photograph  High  Vacuum  Tube  —  Fine 

Focus  82 

104.  Photograph    Gas    Tube  —  Reversed    Po- 

Jaritv   82 


FIG. 
IDS. 

106. 
107. 

108. 

109. 

no. 
III. 
112. 

113- 

114. 

IIS- 
116. 
117. 
118. 
119. 
120. 

121. 
122. 
123. 

124. 

125. 
126. 
127. 
128. 
129. 
130. 
131- 
132. 
133- 
134- 
135- 
136. 
137- 
138- 
139- 

140. 
141. 

142. 
143- 
144- 
145- 
146. 

147- 
148. 
149. 
150. 


Photograph  Broad  Focus,  High  Vacuum 

Tube ^. .  82 

Photograph  Gas  Tube  for  Low  Vacuum  83 
Photograph    Medium    Vacuum    Tube  — 

Fine    Focus  —  Normal    Pressure     ....  84 
Photograph    Medium    Vacuum    Tube — • 

Fine   Focus  —  Abnormal   Pressure....  84 
Diagram    Indicating    Shadows    Cast    by 

Tubes  of  Various  Focus 85 

Pin-Hole  Camera    85 

Roentgenogram  of  Coolidge  Tube 85 

Roentgenogram    of    Target   of    Coolidge 

Tube   86 

Roentgenogram   of   Target   of    Coolidge 

Tube    86 

Screen  Test,  Fine  Focus  Tube 86 

Screen  Test,  Broad  Focus  Tube 87 

Primary.  Scattered  and  Secondary  Rays  87 

Metallic    Iris    Diaphragm 87 

Slit  and  Rectangular  Diaphragm 87 

Effect  of  Simple  Lead  Diaphragm 88 

Effect   of    Varying    Position    of    Diaph- 
ragm    88 

Effect  of  Cylinder  without  Diaphragm.  88 

Effect  of  Cylinder  and  Diaphragm 88 

Effect  of  Diaphragm  between  Recording 

Surface  and  Object 88 

Potter-Bucky  Grating   89 

Potter-Bucky    Diaphragm    89 

Potter-Bucky    Diaphragm    89 

Multiple    Spark    Gap 90 

Valve  Tubes   in   Circuit 90 

Triple  Valve  Tubes  in  Circuit 90 

Oscilloscope  92 

Kilovolt   Spark  Gap   Chart 94 

Sphere   Spinterraeter    94 

Bauer    Qualimeter    95 

Bauer    Qualim.eter    9S 

Benoist   Qualimeter    95 

Benoist  Penetrometer    96 

Wehnelt   Qualimeter    96 

Walter    Qualimeter    96 

Comparative  Scale,  Benoist  and  Benoist- 

Walter pS 

Christen   Penetrometer    99 

Absorption  Curve   for  Rays  of  Various 

Penetration   102 

X-Ray    Spectrum    102 

Photograph   Penetrometer   103 

Radiograph   of   Penetrometer 103 

Radiograph  of  Penetrometer  after  Test.  104 

Radiograph  of  Penetrometer  after  Test.  104 

Radiograph  of  Penetrometer  after  Test.  105 

Tintometer  106 

Holzknecht   Radiometer    108 

Hampson  Radiometer    108 


LIST  OF  ILLUSTRATIONS 


XV 


I'IC.  PAGE 

151.  Double   Trochoscope    114 

152.  Side  View  of  Double  Trochoscope 115 

153.  Operating    Fluoroscope     US 

154.  Fluoroscopic   Screen,   Charlier «. . . .  115 

155.  Holzknecht  Spoon   Compressor 116 

156.  Effects  of  Diversion  and  Parallel  Ray..  117 

157.  Metal    Cylinder    for    Obtaining    Central 

Ray    118 

158.  Tube  Centering  Device  119 

159.  Tube  Centering  Device  119 

160.  Orthofluoroscopic   Apparatus    119 

161.  Orthofluoroscopic   Apparatus    120 

l6ia.     Diagram    Indicating  Principles  of  Stereo- 

Fluoroscopy 120 

Wall-folding   Table    122 

High  Tension  System 123 

High  Tension   Switch 123 

Grounding  of  Accessory  Anode 123 

Regulating  Method,   Gas   Tube 125 

Regulating  Method,   Gas  Tube 125 

Coolidge  Tube  Radiograph  of  very  High 

Penetration   126 

Coolidge     Tube     Radiograph     of     High 

Penetration   126 

Coolidge   Tube  Radiograph   of   Medium 

Penetration    127 

Coolidge     Tube     Radiograph     of     Low 

Penetration    127 

Coolidge  Tube  Radiograph  of  very  Low 

Penetration  128 

Transformer   Chart    128 

Transformer  Chart   129 

Compression  Frame    132 

Method  of   Horizontal  Stereoscopy 132 

Teleroentgenographic    Apparatus 132 

Horizontal   Serial   Apparatus 133 

Plate  Carrier  for  Horizontal  Serial  Ap- 
paratus      133 

Booth  for  Horizontal  Serial  Apparatus.  133 
Plate  Carrier  for  Horizontal  Serial  Ap- 
paratus      134 

Vertical    Serial    Apparatus 134 

Kimoroentgenographic  Apparatus   134 

Roentgenographic   Kymogram    13S 

Biroentgenographic    Apparatus    136 

First    Oblique    Dorso-Ventral    Arrange- 
ment    139 

First    Oblique    Ventro-Dorsal    Arrange- 
ment      139 

Second      Oblique      Ventro-Dorsal      and 

Dorso-Ventral    Arrangement    141 

E.xcentric  Arrangement    142 

Excentric  Arrangement    142 

Illustrating   Radiographic   Axioms 142 

Illustrating   Radiographic   Axioms 143 

Illustrating   Radiographic   Axioms 143 

Illustrating   Radiographic   Axioms 143 


FIG. 

195- 

196a. 

196b. 

197- 

198. 

199. 
200. 

201. 
202. 
203. 
204. 
205. 
206. 
207. 
208. 
209. 
210. 


212. 
213. 
214. 

215- 

216. 

217. 

218 

219 

220. 

221. 
222. 
223. 

224. 

225. 
226. 


P.^GE 

Relation  of  Object  to  Central  Raj- 144 

Relation  of  Object  to  Central  Ray 144 

Relation  of  Object  to  Central  Ray 144 

Compression    by    Cylinder 144 

Compression    by    Cylinder    and    Rubber 

Ball 145 

Immobilization   Device    145 

Relation  of  Diaphragm  Opening  to  Size 

of   Plate   '. 146 

Immobilization  Apparatus    147 

Immobilization  Apparatus    147 

Immobilization  Apparatus    147 

Immobilization  Apparatus    147 

Photograph  of  Head,  Sinuses  Exposed.     148 

Photograph,  Side  View  of  Head 148 

Immobilization  Apparatus    149 

Immobilization  Apparatus    149 

Head  Leveler  150 

Arrangement  for  Antero-Posterior  View 

of    Head    (Occiput)     150 

Arrangement        for        Postero-Anterior 

View  of  Head  (Maxillary  Sinuses)..  151 
Arrangement  for  Infero-Superior  View 

of  Head  (Sphenoidal  Sinuses)    151 

Radiograph  of  Infero-Superior  View  of 

Head   152 

Arrangement  for  Lateral  View  of  Head 

(Sella  Turcica)    152 

Arrangement    for    Oblique    Postero-An- 
terior    View     of     Head     (Sphenoidal 

Sinuses)    I53 

Arrangement    for    Infero-Superior,    Sa- 
gittal  Excentric  View  of   Head    (An- 

cessory    Sinuses)     IS3 

Arrangement         for         Infero-Superior 

Oblique  View  of  Head  (Internal  Ear)  154 
Arrangement         for         Infero-Superior 

Oblique  View   of   Head 154 

Arrangement  for  Infero-Superior 

Oblique  View  of   Head IS4 

Arrangement  for  Supra-Inferior  Frontal 

Excentric  View  of  Head  (Mastoids)  154 
Photograph  of  Head  with  Base  lines...  155 
Arrangement  for  Teeth  Examination...  155 
Direction    of    Central    Ray    (Horizontal 

Film)    156 

Direction     of      Central     Ray      (Oblique 

Film)   156 

Arrangement   for   Examination  of   Teeth 

of  Lower  Jaw   158 

Arrangement  for  Examination  of  Teeth 

of  Upper  Jaw    I59 

Arrangement  for  Examination  of  Teeth 

Horizontal   Film    160 

Extra-oral  Examination  of  Teeth 161 


XVI 


LIST  OF  ILLUSTRATIONS 


FIG. 
22g. 


229a. 

229b. 

230. 
230a. 

231. 

231a. 

232. 

233- 

234- 

235- 

235a. 

236. 

237- 

237a. 

238. 

239- 

239a. 
239b. 
240. 
241. 

242. 

243- 
244. 

245- 
246. 

247. 

248. 
249. 
250. 

251- 
252. 


PAGE 

Arrangement  for  Examination  of  Molar 

Teeth  —  Extra-oral   Examination    ....      161 
Arrangement  for  Examination  of  Bicus- 
pid    and     Molar     Teeth  —  Extra-oral 

Examination   162 

Arrangement  for  Extra-oral  Examina- 
tion of  Bicuspids  and  Molars  on  In- 
clined  Block    162 

The  Spinal  Column 163 

Arrangement    for    the    Examination    of 

Upper  Cervical  Vertebrae 164 

Arrangement    for    Examination    of    the 

Upper    Cervical    Vertebrae 164 

Arrangement  for  Examination  of  Upper 

and  Lower  Cervical   164 

Radiograph  of  the  Lower   Cervical  and 

Upper   Dorsal   Vertebrae 165 

Arrangement  for  Examination  of  Cer- 
vical Vertebrae,  Laterally   165 

Radiograph  of  Lateral  View  of  Cervical 

Vertebrae   165 

Arrangement  for  Excentric  Examina- 
tion of  Dorsal  Spine   166 

Arrangement       for       Examination       of 

Oblique  View  of  Dorsal   Spine 166 

Arrangement  for  Examination  of  Lum- 
bar  Spine   167 

Radiograph  of  Lower  Dorsal  and  Lum- 
bar   Spine    167 

Centering    Point    for    Lateral    View    of 

Lumbar  and  Lumbo-Sacral   Spine....     168 
Arrangement       for       Examination       of 

Lateral  View  of  Lumbar  Spine....     168 
Diagram   of    Pelvis   to    Show    Plane    of 

Inlet  and   Outlet 168 

Diagram   of   Pelvis 169 

Arrangement  for  Radiograph  of  Pelvis.     169 

The  Hip  Joint   171 

Diagram    of    the    Hip    Joint    to     Show 

Parts 171 

Arrangement    for    the    Examination    of 

the  Hip  Joint   171 

Radiograph  —  Lateral  View   of   Hip....     172 
Arrangement       for       Examination       of 

Lateral  View  of  Knee  and  Ankle 172 

Knee   Joint    173 

Arrangement        for        Antero-Posterior 

View   of   Knee I73 

Arrangement      for      Lateral      View      of 

Knee   I74 

Arrangement  for  Oblique  View  of  Knee     174 

Ankle   Joint   I75 

Arrangement        for        Antero-Posterior 

View  of  Ankle  175 

Arrangement     for     Oblique     View     of 

Ankle  176 

Radiograph  —  Oblique  View  of  Ankle..      176 


FIG.  PAGE 

252a.     Apparatus    for    Lateral   View   of   Ankle 

and   Tarsus    176 

253.  Tarsus  ^  . .      177 

254.  Arrangement     for    Supro-Inferior    View 

of   Tarsus    177 

254a.     Infero-Superior  View  of  Feet 177 

255.  Shoulder    Joint ; 178 

256.  Arrangement  for  Examination  of  Acro- 

mio-Clavicular      and      Gleno-Humeral 
Joint 178 

257.  Arrangement        for        Postero-Anterior 

View  of  Gleno-Humeral  Joint 179 

258.  Radiograph   of   Gleno-Humeral   Joint...  179 

259.  Radiograph  of  Acromio-CIavicular  Joint  179 

260.  Radiograph  Showing  Coracoid  Process.  180 

261.  Radiograph     of     Gleno-Humeral     Joint, 

Showing  Humerus    180 

261a.     Diagram   Antero-Posterior   Elbow   Joint  181 

261b.     Diagram   Lateral   View  of   Elbow   Joint  181 

262.  Arrangement    for   Lateral   View   of    El- 

bow  Joint    182 

263.  Radiograph     Oblique     View     of     Elbow 

Joint     182 

264.  Lateral  View  of  Forearm 183 

265.  Postero-Anterior  View   of  Forearm....  183 

266.  Radiograph  to  Show  Carpal  Scaphoid..  184" 

267.  Incorrect   Arrangement    of    Carpus    and 

Metacarpus    184 

268.  Correct    Arrangement    for    Postero-An- 

terior   View    of    Carpus     and     Meta- 
carpus        184 

269.  Arrangement   for   Examination   of   Pos- 

tero-Anterior    View     of     Chest-Hori- 
zontal       185 

270.  Arrangement    for    E-xamination    of    An- 

tero-Posterior   View    of    Chest-Hori- 
zontal        185 

271.  Arrangement  for  First  Oblique  Ventro- 

Dorsal  View  of  Chest  —  Horizontal..      187 

272.  First    Oblique    Dorso-Ventral    View    of 

Chest-Vertical  187 

273.  Lateral  View  of  Chest 188 

274.  Tracing    of    Radiograph,    First    Ventro- 

Dorsal  View  Showing  Esophagus....  188 
27s.       Radiograph  Ventro-Dorsal,  First 

Oblique  View  of  Chest 189 

276.       Radiograph     Showing     Gastro-Intestinal 

Tract , 189 

2-/J.       Radiograph       Showing      Gall       Bladder 

Region  191 

278.  Arrangement    for    Examination    of    the 

Urinary  Tract  by  Four  Exposures 192 

279.  Arrangement   for   Examination   of   Kid- 

ney and  Upper  Ureters 192 

280.  Radiograph     of     Kidneys     and     Upper 

Ureters    192 


LIST  OF  ILLUSTRATIONS 


xvn 


FIG. 
281. 


283. 


284. 

285. 
286. 


290. 
291. 
292. 

293- 
294. 

295- 


PAGE 

Arrangement       for       Examination       of 

Urinary  Tract  by  Six  Exposures 193 

Arrangement       for       Examination       of 

Urinary  Tract  by  Six  Exposures 193 

Arrangement       for       Examination       of 

Bladder  —  Antero-Posterior    194 

Arrangement       for       Examination       of 

Bladder  —  Postero-Anterior   194 

Automatic  Time  Switch  and  Breaker...  197 

Section  of  X-Ray  Film 190 

Section  of  X-Ray  Film 199 

Section   of   Photographic    Film 210 

Section    of    Photographic    Film 210 

Tank    Developing    System 211 

Method  for  Drying  Dental  Films 211 

Illuminating    Box  —  Reflected    Light....  213 

Illuminating  Box  —  Transmitted  Light.  213 
Illuminating     Box  —  Reflected     Light  — 

Cooper    Hewitt    213 

Illuminating     Box  —  Transmitted     Light 

—  Cooper  Hewitt    214 


FIG.  PAGE 

296.  Revolving  Illuminating  Box 214 

297.  Filing  Case  for  Lantern  Slides 215 

298.  Prism    Stereoscope    215 

299.  Reflecting   Stereoscope    215 

300.  Single   Alirror    Stereoscope 215 

306.  Plan   of   X-Ray   Laboratory 223 

302.  Requisition   Card   220 

303.  Diagnosis   Card    221 

304.  Daily  Record   Card    222 

305.  Plan    X-Ray    Laboratory 223 

306       Plan  of  X-Ray   Laboratory 223 

307.  Plan      of      Bellevue      Hospital      X-Ray 

Laboratory  224 

308.  Radiographic      Room  —  Bellevue      Hos- 

pital      225 

309.  Fluoroscopic      Room  —  Bellevue      Hos- 

pital     226 

310.  Fluoroscopic      Room  —  Bellevue      Hos- 

pital      227 

311.  Serial    Room  —  Bellevue    Hospital 229 


PART  I 

THE  PRINCIPLES  OF 

TECHNIQUE 


The  Principles  and  Practice  of  Roentgenogical 
•  Technique 


PART  I 


CHAPTER  I 
I'RINCIPLES  OF  ELECTRICITY 

The  nature  of  electricity  is  unknown.  It 
is  capable  of  producing  certain  peculiar  phe- 
nomena, manifesting  itself  by  attractions  and 
repulsions,  by  luminous,  heating  and  chemical 
effects  and  by  violent  disturbances  as  lightning. 
It  may  reveal  itself  as  a  charge  residing  on  the 
Burface  of  a  body  or  as  a  current  flowing 
through  its  substance. 

Electricity  is  a  medium  for  the  transmission 
of  energy.     It  is  not  energy  itself. 

Electron  Theory.  The  generally  accepted 
modern  theory  of  electric  phenomena  is  that 
they  are  due  to  movement  of  electrons.  Ac- 
cording to  this  theory  the  atom  which  until 
recently  was  considered  the  smallest  particle 
of  matter,  may  be  further  subdivided.  It  is 
now  said  to  consist  of  a  positive  electrical 
charge  surrounded  by  very  much  smaller  par- 
ticles of  negative  electricity — called  electrons. 
All  of  the  ninety-two  different  kinds  of  atoms 
(which  embraces  all  matter)  are  similarlv 
made  up.  Though  the  positive  nuclei  of  dis- 
similar atoms  apparently  differ,  all  electrons 
are  alike.  The  number  of  electrons  in  dis- 
similar atoms  varies.  Thus  hydrogen  has  one 
electron,  while  helium  has  ninety-two.  The 
heavier  atoms  or  elements  have  more  electrons 
than  the  lighter  but  there  are  the  same  num- 
ber of  electrons  in  equal  mass  of  every  kind 
of  matter.  The  electron  is  the  smallest  quan- 
tity of  electricity  transferable  from  one  atom 
to  another  and  capable  of  existing  alone.  All 
electrons  have  the  same  size,  mass  (weight) 
and  embody  the  same  (pumtity  of  electricity. 
The  diameter  of  an  electron  is  about  140,000 
times  smaller  than  that  of  the  hydrogen  atom. 
It  has  been  graphically  pointed  out  that  the 


size  of  the  electron  is  to  the  size  of  the  tu- 
bercle bacillus  as  the  bacillus  compares  in  size 
to  the  earth.  The  weight  of  an  electron  is 
about  1/1800  of  the  hydrogen  atom  or  a 
forty-sixth  billion,  billion  billion  billionth  of 
an  ounce.  The  quantity  of  electricity  of  an 
electron  is  1/455000000000000000  of' a  coul- 
omb. The  electrons  are  arranged  about  the 
positive  nucleus  of  the  atom  in  definite  sys- 
tems and  travel  in  definite  orbits.  The  ar- 
rangement has  been  styled  an  "  infinitesimally 
small  solar  system."  The  electrons  are  not 
compactly  crowded  into  the  atom,  in  fact,  the 
spaces  between  them  as  compared  to  their  size 
is  relatively  as  great  as  the  spaces  between 
the  planets  in  the  solar  system.  Carrying  sim- 
ilar negative  charges,  the  electrons  repel  each 
other  with  relatively  enormous  force  and  sep- 
arate as  far  as  possible  from  each  other,  un- 
less restrained  by  some  counter  force.  It  has 
been  estimated  that  if  two  equal  spheres  of 
electrons  each  weighing  one  gram  were  placed 
one  centimeter  apart  they  would  repel  each 
other  with  a  force  equal  to  320,000,000,000.- 
000,000,000,000,000  tons.  The  electrons  are, 
therefore,  in  constant  movement,  while  still 
a  part  of  the  atom,  and  are  maintained  within 
their  orbits  by  the  attractive  force  of  the 
positive  nucleus,  which  neutralizes  in  the  nor- 
mal atom  the  total  negative  charge  of  the  elec- 
trons and  the  particular  substance  thus  ex- 
hibits no  evidence  of  electrification. 

There  is,  however,  considerable  dift'erence 
in  the  force  by  which  the  electrons  are  held 
in  the  particular  atom.  In  some  matter  the 
electrons  are  bound  in  the  atom  by  such  a 
powerful  restraining  power  that  they  can  be 
separated  only  with  great  difficulty  or  not  at 
all.     In  other   substances,   the  electrons   mav 


[1] 


ELECTRONS 


be  separated  with  comparative  ease.  \\'hen 
any  physical  or  chemical  change  breaks  down 
the  connection  between  an  electron  and  the  re- 
mainder of  the  atom,  the  released  electrons 
may  shoot  away  with  tremendous  velocity. 
The  disintegrating  force  may  cause  the  elec- 
tron to  jump  from  one  orbit  to  the  next  at 
high  speed,  thus  setting  up  vibrations  in  the 
ether.  The  waves  set  up  become  manifest  to 
the  senses  as  radiant  heat  and  light. 

On  the  other  hand  the  disintegrating  force 
may  be  more  powerful  and  the  electrons  may 
leave  the  atom  and  exist  in  a  free  state  carry- 
ing a  negative  electrical  charge.  The  positive 
nucleus  is  unknown  in  a  free  state. 

Such  streams  or  torrents  of  electrons  are 
called  cathode  rays.  The  electron  is  able  to 
respond  to  electric  force  and  to  acquire  great 
velocity  under  such  force.  Sudden  changes 
in  velocity  of  the  electron  result  in  ether 
disturbances.  The  impact  of  such  a  stream 
of  electrons  under  certain  electrical  conditions 
in  a  vacuum  tube  against  an  atom  will  cause 
tremendous  ether  disturbances  and  the  prop- 
agation of  waves  of  very  high  frequency, 
some  of  which  constitute  that  form  of  energy 
known  as  x-rays. 

The  term  ray  is  therefore  applied  either 
to  particles  the  result  of  atomic  disintegration 
as  the  stream  of  electrons  above  described 
(cathode  rays),  or  to  the  transfer  of  physical 
effects  by  the  agency  of  wave  motion,  as  the 
x-rays  or  gamma  rays  both  having  their 
origin  in  electronic  torrents. 

Slow-moving  electrons  are  emitted  by  met- 
als when  exposed  to  light  or  ultraviolet  rays. 
The  beta  rays  of  radium  are  fast-moving  elec- 
trons, which  are  emitted  constantly  by  radium 
because  the  arrangement  of  the  electrons  in 
the  radioactive  atoms  is  an  unstable  one. 
Since  the  properties  of  a  particular  substance 
are  determined  by  the  number  and  grouping 
of  the  electrons,  the  properties  of  these  radio- 
active substances  change  as  a  result  of  con- 
stant electron  emanation  into  another  variety 
of  atom.  Thus  radium  by  the  loss  of  elec- 
trons may  change  into  helium. 

In  ordinary  substances,  however,  the  elec- 


trons which  can  be  removed  constitute  only  a. 
very  small  percentage  of  the  atomic  posses- 
sion, one  in  a  million  millions,  but  because  of 
the  enormous  repulsive  powers  of  the  elec- 
trons, even  this  small  number  is  capable  of 
giving  rise  to  many  phenomena. 

It  has  been  stated  that  normally  atoms  ex- 
hibit no  electrical  properties  because  the  posi- 
tive electricity  in  them  is  neutralized  by  the 
negative.  But,  if  the  balance  is  disturbed  by- 
adding  or  subtracting  electrons,  electrical 
properties  manifest  themselves.  For  when, 
electrons  are  set  in  motion  and  caused  to  move 
from  one  location  to  another  they  produce-  ■ 
what  are  known  as  electric  phenomena. 

The  atoms  concerned  in  these  changes  are 
said  to  be  ionized,  and  that  atom  from  which 
the  electron  has  been  taken  and  the  one  to 
which  it  has  been  added  are  charged  particles- 
called  ions.  If  the  ion  is  the  result  of  sub- 
traction of  an  electron  it  is  called  a  positive 
ion,  if  the  result  of  the  addition  of  an  electron 
it  becomes  a  negative  ion.  Thus  a  substance 
having  an  excess  of  electrons  is  negatively 
charged  or  electrified,  but  vi^hen  it  has  less 
than  the  normal  quota  it  is  positively  charged 
or  electrified.  Bodies  charged  with  the  same 
electricity  repel  each  other  while  those  charged 
with  opposite  electricity  attract  each  other. 
For  an  atom  which  has  an  excess  will  repel 
any  other  atom  which  has  an  excess  but  at- 
tract an  atom  which  has  a  deficit  or  a  normal 
number  of  electrons. 

Generators,  dynamos,  batteries  or  other  de- 
vices do  not  generate  electricity  but  only  are 
agencies  whereby  the  electron  already  in  ex- 
istence is  forced  to  move.  These  devices  then 
furnish  only  pressure  or  force  (electro-motive 
force)  to  move  electrons  and  when  electrons 
move  there  is  an  electric  current.  Since  the 
electron-current  fiows  from  a  point  of  higher 
to  a  point  of  lower  pressure  it  follows  that 
the  terminal  of  the  energy-delivering  device 
fron-i  which  the  electron-current  flows  is  the 
negative  pole,  while  the  positive  terminal  of 
the  delivering  device  is  the  one  into  which  the 
electrons  flow. 


CONDUCTORS 


The  common  methods  by  which  electro-mo- 
tive forces  may  be  developed  are : 

1.  By  contact  of  dissimilar  substances. 

a )   through  chemical  action 
h)    or  the  application  of  heat. 

2.  By     electro-magnetic     induction.       The 

dynamo    is    a    generating    instrument 
built  on  this  principle. 

3.  By    dielectric    flux    "  static    electricity " 

generated  by  a  static  machine  by  fric- 
tion of  dissimilar  substances. 
The  commonly  utilized  methods  are : 

1.  By  contact  of  dissimilar  metals  through 

chemical  action. 

2.  By  electro-magnetic  induction. 

Conductors  and  Insulators:  Every  substance 
/iffers  more  or  less  resistance  to  the  passage 
of  an  electric  current  through  it.  The  posses- 
sion of  this  property  to  a  variable  degree  ena- 
bles us  to  classify  those  substances  as  con- 
ductors, which  ofifer  but  minimum  resistance, 
semi-conductors,  which  ofifer  a  medium 
amount  of  resistance,  and  non-conductors  or 
insulators,  which  ofifer  comparatively  great 
resistance.  No  substance  known  is  an  abso- 
lute non-conductor  of  electricity. 

The  reciprocal  of  conductivity  is  resistance. 
A  conductor  surrounded  or  supported  by  a 
non-conductor  is  said  to  be  insulated. 

Insulating  substances  may  be  considered  as 
substances  in  which  the  electrons  are  held 
tightly  bound  in  the  atoms  and  prevent  the 
flow  or  movement  of  electrons,  hence  the  pas- 
sage of  currents.  Conductors  would,  accord- 
ing to  this  theory,  be  substances  in  which  the 
electrons  are  held  rather  loosely  in  their  atoms 
and  can  be  readily  moved  by  the  application 
of  electric  pressure  or  voltage. 

Table  of  Substances  in  Order  of  Their 
Conductivity 

Conductors  Non-conductors 

Metals  Dry  o.xides 

Carbon  Fat 

Coal  Ashes 

Graphite  .  Ice  at  — 25°C. 

Acids  Phosphorous 


Conductors 
Water — salt 
Vegetable  matter — 

living 
Animals 
Soluble  salts 

Semi-conductors 
Alcohol 
Cotton 
Ether 

^^'ood — dry 
Marble 
Straw 

Water — distilled 
Paper 
Ice  at  0"C. 


Non-conductors 

Chalk 

Rubber 

Dry  air 

Etheric  oils 

Porcelain 

Leather 

Wool 

Silk 

Mica 

Jewels 

Glass 

Wax 

Paraffin 

Resins 

Sulphur 


Forms  of  Electricity:  Electricity  may  be 
at  rest,  existing  as  "  charge ;"  or  in  motion,, 
current  electricity.  Electrons  in  rotation  pro- 
duce the  phenomena  known  as  magnetism. 
Electricity  in  rapid  oscillation  exhibits  prop- 
erties dififering  from  those  manifest  in  any  of 
its  previous  states,  and  results  in  the  propaga- 
tion of  radial  wave  motion. 

Charging  by  Contact:  An  insulated  con- 
ductor may  be  charged  with  electricity  from 
an  electrified  body  by  simple  contact  and  will 
retain  this  electric  charge  which  spreads  over 
its  entire  sm-face  from  the  point  of  contact 
for  an  indefinite  time  providing  the  insulation 
is  maintained.  Should  this  conductor,  so- 
charged,  be  touched  by  a  body  connected  with 
the  earth,  it  will  at  once  lose  this  charge  and 
be  discharged,  the  electricity  flowing  into  the 
earth.  In  other  words  the  charge  has  been 
"grounded"  or  "earthed." 

Actual  contact  is,  moreover,  not  essential  r 
for,  if  an  electrified  body  is  brought  near  an 
insulated  imelectrified  conductor  it  induces, 
electricity  upon  the  latter,  an  opposite  charge 
on  the  near  side  and  a  like  on  the  far  side. 
This  is  called  electrostatic  induction.  When 
two  oppositely  charged  bodies  are  placed  near 
each  other,  the  space  between  them  is  called 
an  electric  field  and  has  acting  across  it  lines 
of  electric  force.     The  tension  which  exists  in 


ELECTRICAL  TERMS 


this  field  tends  to  draw  the  two  surfaces  to- 
gether. 

Charging  by  Induction — Tension — Poten- 
tial— Current:  By  repeated  contact  insulated 
bodies  may  be  charged  with  more  or  less  elec- 
tricity. L'pon  the  body  charged  with  more, 
the  electricity  will  therefore  exist  under 
greater  tension  or  pressure  than  upon  the 
body  charged  with  less,  so  that  there  will  be 
electrically  speaking,  a  difference  of  tension 
between  two  such  bodies. 

If  two  charged  conductors  having  this  ten- 
sion or  potential  dift'erence  are  connected  by 
a  third  conductor,  as  a  piece  of  wire,  the  elec- 
tricity will  naturally  flow  from  the  conductor 
upon  which  it  exists  under  greater  tension  to 
the  one  where  the  tension  is  low,  and  an  elec- 
tric current  will  thus  be  established  which  will 
be  maintained  until  the  dift'erence  of  tension 
or  potential  is  equalized. 

An  electric  current  is,  therefore,  electrons 
in  motion.     The  flow  must,  according  to  the 
electron  theory,  be  from  negative   (the  atoms 
in  which  the  electrons  are  in  excess)   to  the 
positive  (where  there  is  a  deficit  of  electrons). 
As  long  as  the  e.  m.  f.  is  applied  to  a  con- 
ducting    path,     an     atom     will     receive     an 
electron    from    the    adjoining    atom    and  pass 
one    on    to    its    neighbor    on    the    other    side. 
When   the   force   is   removed   the   current  or 
flow  of  electrons  will  cease,  that  is  to  say  the 
transference  of  the  electrons  from  one  atom 
to  another  will  cease.     This  transference  will 
take  place  because  the  impelling  force  is  act- 
ing in  a  structure  whose  material  is  such  that 
the  atoms  can  readily  give  and  take  electrons, 
in  other  words  a  conductor.     If  the  conduct- 
ing path  is  incomplete,  the  pressure  may  still 
exist  but  without  flow  or  current  of  electricity. 
Electro  Motive  Force:     The    tendency    or 
force   by   which   electricity   is   impelled   from 
the  one  body  to  another  is  the  electro-motive 
force  or  voltage.     The  greater  the   potential 
difference  the  greater  will  be  the  electro-mo- 
tive  force  or   pressure   impelling  the   current 
from  one  conductor  to  the  other.     A  higher 
voltage  would   be   required   to    force   a   given 
amount    of    electricity    through    a    small    con- 


ductor than  through  a  large  one  in  a  given 
time.  Generators  separate  the  negative  from 
the  positive  charges  of  the  atom,  and  it  is  this 
tendency  of  the  charges  to  come  together 
which  is  expressed  in  volts. 

Voltages  below  1,000  may  be  said  to  be 
"  low  tension."  In  x-ray  work  the  low  ten- 
sion voltages  which  we  use  are  all  less  than 
250.  AA'ith  low  voltages  all  connections  must 
be  tight  or  soldered,  the  wires  must  be  large, 
so  that  they  offer  little  resistance  to  the  low 
pressure  and  corresponding  high  amperage 
necessary  to  transmit  a  large  amount  of  en- 
ergT  and  no  part  of  the  circuit  need  be  heav- 
ily insulated  in  order  to  be  safe  to  touch. 

Voltages  above  1,000  may  be  said  to  be 
"  high  tension."  In  x-ray  work,  the  high  ten- 
sion voltages  range  from  25,000  to  100,000. 
Such  extremely  high  pressure  is  able  to  send 
current  through  ordinary  substances  offering 
resistance,  to  low  tension  voltage.  For  ex- 
ample, though  200  volts  will  not  send  current 
through  air,  100,000  volts  will  force  current 
through  nine  inches  of  air.  This  means  that 
fine  wire  will  not  oft'er  much  resistance  and 
can  be  used  for  transmitting  high  voltage. 

Connections  need  not  be  tight  nor  soldered, 
because  high  tension  will  pass  through  poor 
connections.  The  wires  carrying  high  tension 
are  dangerous  if  approached,  or  if  touched. 
They  should  be  heavily  insulated.  For  con- 
venience, we  call  1,000  volts  a  kilo-volt; 
100,000  volts  is  called  100  K.  V. 

The  volt  expresses  dift'erence  in  pressure 
and  the  expression,  potential  dift'erence,  has 
the  same  meaning,  for  it  is  not  the  potential 
but  the  dift'erence  in -potential  which  causes 
the  electricity  to  flow  and  the  flow  will  con- 
tinue until  the  potential  is  equalized. 

Resistance:  (OHM).  Depending  on  the 
material  employed  every  substance  offers  more 
or  less  resistance  to  the  passage  of  electricity 
and  this  resistance  is  proportional  to  the  length 
and  inversely  proportional  to  the  cross  section- 
al area  of  the  conductor.  Thus,  doubling  the 
thickness  of  a  wire  would  bring  its  resistance 
down  to  1/4  for  the  same  length. 

The  unit  of  this  resistance  is  an  ohm.  which 


OHM'S  LAW 


is  equivalent  to  the  resistance  oiTered  by  a 
copper  wire  250  feet  long  and  1/20  inch  in 
diameter  or  a  column  of  Hg  at  32°F.  which 
is  of  one  square  millimeter  section  and  1.06 
meters  in  length. 

The  magnitude  of  the  current  passing 
through  a  given  circuit  will  depend  on  the 
pressure  or  voltage  and  on  the  resistance  of 
the  conductors.  The  magnitude  of  current 
passing  through  a  given  circuit  may  be  con- 
trolled by  varying  the  resistance,  for  this  re- 
acts on  the  voltage.  Increasing  resistances 
uses  up  voltage  and  thus  diminishes  the  quan- 
tity. In  practice  this  is  done  by  instruments 
called  rheostats.  The  form  commonly  used 
consists  of  a  series  of  coils  of  German  silver 
wire,  which  has  great  resistance,  fixed  and 
insulated  in  a  frame,  with  the  means  for 
throwing  one  or  more  of  these  coils  into  the 
circuit.  The  strength  of  the  current  is  dimin- 
ished by  compelling  it  to  travel  through  many 
of  these  coils  or  increased  by  cutting  the  coils 
out  of  the  circuit.  Heat  is  produced  by  a 
current  flowing  through  a  resistance. 

Quantity — {Coulomb) :  Quantity  is  the 
amount  of  electricity  developed  from  any 
source.     Its  unit  of  measure  is  a  coulomb. 

Strength  Rate  of  Flozv — [Ampere):  An 
electric  current  is  estimated  by  stating  its  rate 
of  flow  or  the  number  of  coulombs  passing 
through  a  given  conductor  in  a  unit  of  time, 
as  a  stream  of  water  may  be  described  by 
stating  the  number  of  quarts  passing  through 
a  given  pipe  per  second.  When  the  quantity 
passing  is  one  coulomb  per  second  the 
strength  is  one  ampere,  which  is  the  unit  of 
the  rate  of  flow  of  the  current.  Thus,  4 
amperes  will  transfer  40  coulombs  in  10  sec- 
onds. A  thousandth  of  an  ampere  is  called 
a  milliampere. 

Ohm's  LazK.':  The  strength  of  the  current 
varies  in  direct  proportion  with  the  electro- 
motive force  and  in  inverse  proportion  to  the 
resistance.  In  other  words,  the  ratio  of  the 
electro-motive  force  to  the  current  strength 
in  a  given  circuit  is  a  constant  which  may  be 
called  the  resistance  of  the  circuit. 

If   the  current  strength   is   indicated  by   I, 


the  voltage  or  electromotive  force  by  E  and 
the  resistance  by  R,  the  relations  may  be  ex- 
pressed symbolically  as 

E 


I=^orE=IxRorR 


I 

This  is  known  as  Ohm's  Law.  This  law 
does  not  hold  where  gaseous  conductors  are 
concerned,  then  the  ratio  of  e.m.f.  to  current 
depends  on  the  strength  of  the  latter.  One 
volt  sends  one  ampere  through  one  ohm. 

It  has  already  been  pointed  out  that  voltage 
or  pressure  may  exist  without  current.  Vol- 
tage or  potential  difference  by  itself  is  futile 
as  far  as  accomplishing  anything  electriaal 
is  concerned.  Current  (amperage)  is  neces- 
sary, but  it  is  the  voltage  which  makes  current 
and  the  rate  of  flow  of  the  current  or  am- 
perage will  depend  on  the  pressure  divided, 
by  the  resistance.  The  volt  is  that  ditlerence 
in  electrical  pressure  which  will  maintain  a 
current  of  1  ampere  through  a  resistance  of 
1  ohm. 

Ohm's  Law  may  be  applied  to  a  whole  or 
a  part  of  a  circuit ;  that  is  to  say,  the  current 
in  a  certain  part  of  the  circuit  equals  the 
voltage  across  the  same  parts,  divided  by  the 
resistance  of  that  same  part. 

Thus,  if  to  a  generator  which  is  able  to 
supply  a  pressure  of  200  volts  at  no  load 
there  is  connected  a  copper  circuit  of  negli- 
gible resistance,  in  which  are  two  pieces  of 
German  silver  wire,  one  of  18  ohms  resistance 
and  one  of  1.9  ohms  resistance  and  the  wind- 
ings of  the  generator  have  .1  ohms  resistance, 
the  amount  of  current  the  200  volts  pressure 
is  able  to  force  through  the  18 -|- 1.9 -(- .1 
ohms  resistance  may  be  estimated  by  applying 
Ohm's  Law,  E=IR  where  E  is  voltage,  I  is 
amperage  and  R  is  ohms  resistance.  In 
this  case  200  =  I  X  20.  Therefore  I  =  10. 
Knowing  the  amperage  in  the  circuit,  the  vol- 
tage lost  in  each  of  the  resistances  may 
be  determined  by  this  same  law.  For  ex- 
ample, since  10  amperes  is  flowing  through 
the  18  ohm  unit,  then  E=  10X18  =180. 
Therefore,  ISO  volts  is  lost  or  used  up  in  this 
unit;  10  amperes  is  flowing  through  1.9  ohm& 


6     DE\^ELOPMENT  OF  ELECTRO-MOTIVE  FORCE  BY  CHEMICAL  ACTION 


then  E:=  lOX  L9=  19  volts  lost  in  the  sec- 
ond unit  and  similarly  1  volt  is  lost  in  the 
generator.     Thus,    180  +  19  +  1  =  200. 

i 


\ __. f^es'iro'Ke  =  0.3  Of" 


Fig.  I 

Ohm's  law  is  useful  to  determine  how  much 
-current  a  given  voltage  will  force  through  a 
given  resistance,  or  how  much  voltage  will  be 
needed  to  force  the  current  through  a  given 
resistance ;  or,  given  a  voltage  and  knowing 
the  current,  the  amount  of  resistance  in  the 
•circuit  may  be  ascertained  and  consequently 
the  size  of  the  wire  needed  to  prevent  too 
much  voltage  loss  may  be  determined. 

Pozvcr  {ivatt).  The  watt  is  the  power  or 
the  amount  of  energy  developed  by  a  current 
of  one  ampere  flowing  under  a  pressure  of 
one  volt.  The  product  of  amperes  multiplied 
by  volts  equals  watts  as  a  symbol  of  power. 
One  kilo-watt  equals  1,000  watts  which  is  ap- 
proximately ly^  horse-power.  One  kilo- watt 
maintained  for  one  hour  is  called  a  kilo-watt 
hour. 

The  above  rule  may  be  expressed  as  fol- 
lows : 

■   P  =  IXE  (1) 


But  I  = 


E_ 
R 


(see  above) 


-(2) 


Therefore  V=^X  '£-=-  — 
^  R 


Electromotive  force  squared 

■or   Power   in   W'atts;^ 

Resistance  in  Ohms 
Also  since  E  =  I  XR 

P=:IXIXR  or  P  =  PXR  —(3) 
or  Power  in  Watts  =  Current  in  amperes 
squared  multiplied  by  resistance  in  ohms. 


Thus  if  it  is  desired  to  know  how  many 
watts  are  consumed  in  the  transmission  lines 
to  a  non-inductive  load,  (direct  current  ^notor, 
Fig.  1)  if  the  current  in  the  line  wires  is  40 
amperes  and  the  resistance  in  each  lead  is  0.3 
ohms,  the  formula  would  be 

P  =  PXR   or  P  =  40=  X  (0.3  +  0.3) 
1600X0.6=960  Watts 

Under  these  conditions  there  would  be  a 
loss  of  24  volts  (40X0.6).  If  the  original 
voltage  were  220,  the  total  available  at  the 
motor  would  be  196.  or  if  the  line  voltage  is 
220  and  the  current  40  amperes  the  watts  con- 
sumed by  a  D.  C.  motor  would  be  obtained  by 
the  formula 

P  =  I  X  E,  or  40  X  220  =  8800  watts  or 
8.8  kilowatts,  or  1/746X8800=10.5  horse- 
power 

The  above  three  equations  express  the 
equivalents  of  power  in  direct  current  cir- 
cuits and  in  alternating  current  circuits  if  the 
connected  load  is  non-inductive,  but  where  in- 
ductive loads  such  as  alternating  current  mo- 
tors, transformers,  arc  lamps  (incandescent 
lamps  are  non-inductive)  exist  the  product  of 
eiTective  volts  and  effective  amperes  in  a  cir- 
cuit must  be  multiplied  by  a  power  factor  to 
obtain  the  true  power  in  watts.  This  power 
factor  is  expressed  as  a  percentage.  The 
power  factors  for  motors  is  80%,  for  arc 
lamps  87%. 

P  (True  Power)  =IX  EX  P-f- 
If  it  is  desired  to  know  the  actual  power 
taken  by  an  alternating  current  circuit  feeding 
a  motor,  the  impressed  voltage  being  220,  the 
current  22.5  amperes  and  the  power  factor  of 
the  load  85%,  the  formula  would  be 

P  =  I  X  E  X  P-   f  •  or 
22.5X220X0.85  =  4.2  K.  W. 

1.  The  Developuient  of  Electromotive 
Forces  by  Chemical  Action.  If  two  different 
metals  are  brought  into  contact  with  each 
other  or  immersed  in  a  liquid,  one  becomes 
electrically  positive  and  the  other  negative  and 
a  difference  of  potential  is  found  to  exist  be- 
tween  them.      The   liquid   in   which   the   dis- 


VOLTAIC  CELL 


:similar  metals  are  introduced  must  be  capable 
-of  reacting  chemically  with  one  of  them,  and 
is  called  an  electrolyte.  This  potential  differ- 
ence is  a  definite  and  constant  phenomenon 
and  depends  upon  one  factor  only — the  nature 
of  the  metals  and  liquids  concerned  in  the 
■combination.  This  combination  of  two  differ- 
ent metals  and  an  electrolyte  converts  chemi- 
cal action  into  an  electrical  current,  and  is 
called  a  galvanic  element  or  cell.  All  the 
e.  m.  f .  developed  by  a  voltaic  cell  is  generated 
at  the  area  of  contact  between  the  electrolyte 
and  the  positive  electrode  or  anode. 

If  the  two  metals  with  this  potential  differ- 
■ence  are  connected  by  means  of  a  conductor, 
the  electricity  will  flow  from  the  metal  with 
the  higher  potential  through  the  conductor  to 
the  metal  with  the  lower  potential  with  the 
tendency  to  equalize  their  tensions. 

In  this  voltaic  element,  however,  the  chemi- 
■cal  action  in  the  cell  being  continuous,  the 
production  of  electricity  is  constant  and  the 
■same  potential  difference  is  constantly  rees- 
tablished and  maintained  through  the  agency 
•of  the  connecting  conductors  so  that  the  equal- 
izing process  never  actually  occurs  and  the 
continuous  current  is  thus  established  which 
was  long  known  as  the  galvanic  current.  The 
tension  difference  is  the  electromotive  force 
or  voltage  of  the  particular  cell. 

If  a  cell  be  constructed  by  immersing  a 
•plate  of  copper  and  one  of  zinc,  in  a  compoimd 
fluid  capable  of  reacting  chemically  with  one 
■of  the  metals,  as  a  solution  of  sulphuric  acid, 
and  if  the  ends  of  the  metal  plates  called  their 
poles  or  electrodes  be  connected  by  a  strip  of 
■copper  wire,  chemical  action  will  manifest  it- 
self by  the  generation  of  bubbles  of  gas  which 
will  collect  about  the  copper  plate.  The  bub- 
bles of  gas  consist  of  hydrogen  which  results 
from  the  reaction  between  the  zinc  and  the 
sulphuric  acid  with  the  formation  of  the  solu- 
iDle  zinc  sulphate.  It  is  thus  that  the  potential 
•energy  of  chemical  separation  between  the 
zinc  and  the  acid  is  transformed  into  kinetic 
■or  manifest  energy  of  two  kinds — heat  and 
electricity.  The  zinc  is  the  generating  or  anode 
element  while  the  copper  is  the  collecting  or 


cathode  element,  but  the  flow  of  electricity  is 
from  the  negative  to  the  positive  element  in 
the  liquid.  If  the  terminal  of  the  copper  plate 
and  the  terminal  of  the  zinc  plate  are  con- 
nected by  a  piece  of  wire,  the  electricity  would 
then  flow  (in  the  air)  from  the  zinc  plate 
terminal  (which  is  now  the  negative  pole) 
across  the  wire  to  the  copper  plate  terminal 
(which  is  the  positive  pole).  (Electronic 
Theory.)  This  path  traversed  by  the  current 
is  its  circuit.  While  the  electrodes  are  con- 
nected by  the  conductor  the  circuit  is  closed, 
the  chemical  action  continues  and  electricity  is 
generated.  \Mien  the  connection  is  discon- 
tinued the  circuit  is  broken  or  open  and  the 
production  of  electricity  ceases  though  the 
potential  difference  established  by  immersing 
the  plates  in  the  acid  still  exists.  The  absolute 
value  of  the  e.m.f.  of  the  cell  depends  only  on 
the  zinc  and  copper  plates  and  the  acid 
(chemical  relations),  not  on  the  size  or  quan- 
tity of  either.  The  maximum  e.m.f.  is  obtained 
in  those  combinations  where  the  electrodes  are 
zinc  and  carbon. 

Voltaic  Battery:  A  number  of  galvanic  cells 
so  connected  to  each  other  that  the  current 
flows  in  the  same  direction  in  all,  constitutes 
a  voltaic  battery.  The  battery  may  consist 
of  a  greater  or  smaller  number  of  cells  depend- 
ing upon  the  amount  of  energy  required.  But 
besides  their  number,  their  arrangement  has 
much  to  do  with  the  strength  and  tension  of 
the  electric  output. 

Resistance  of  Voltaic  Cells:  In  the  utiliza- 
tion of  the  voltaic  cell  there  are  two  kinds  of 
resistance  to  be  considered,  the  internal  resist- 
ance within  the  cell  liquid  and  the  external 
resistance  within  the  wire  circuit. 

The  greater  the  distance  between  the  metal- 
lic plates  in  the  liquid,  the  greater  will  be  the 
internal  resistance,  and  the  greater  the  sectional 
area  of  the  plates  the  less  will  be  its  resistance. 
The  internal  resistance  is  also  increased  by  the 
adherence  of  bubbles  of  hydrogen  gas  to  the 
negative  (Copper)  plate  because  the  gas  being 
a  poor  conductor  diminishes  the  chemically 
effective  area  of  the  plate.  The  external  re- 
sistance in  the  wire  circuit  depends  upon  fac- 


STORAGE  CELL 


tors  already  considered.  The  maximum  cur- 
rent is  attained  when  the  resistance  of  the  ex- 
ternal circuit  is  made  equal  to  the  internal  re- 
sistance of  the  battery.  Batteries  may,  there- 
fore, be  arranged  for  great  external  resistance. 
For  small  external  resistance  the  cells  may  be 
so  connected  as  to  have  small  internal  resis- 
tance. 

Connecting  in  Scries:  When  the  positive 
pole  of  one  cell  is  connected  to  the  negative 
pole  of  another  and  so  on,  the  total  electro- 
motive force  of  such  a  battery  is  the  sum  of 
the  electromotive  forces  of  all  the  cells  in  the 
combination.  Cells  so  combined  are  joined  in 
series.  The  resistance  of  such  a  battery,  how- 
ever, is  also  the  sum  of  the  resistance  of  each 
cell  in  the  combination  and  such  a  battery  is 
called  a  battery  of  high  internal  resistance  and 
is  needed  for  a  circuit  vi^hich  has  high  external 
resistance  because  high  electromotive  force  is 
generated. 

Connecting  in  Parallel:  In  this  method  all 
the  positive  plates  are  connected  on  one  side 
and  all  the  negative  plates  on  the  other.  Such 
a  combination  is  called  a  battery  of  low  in- 
ternal resistance.  The  electromotive  force  of 
such  a  battery  is  that  of  a  single  cell  because 
this  depends  on  the  nature  of  the  metals  only, 
but  the  resistance  is  low,  being  that  of  a  single 
cell  divided  by  the  number  of  cells  in  the  bat- 
ter\^  because  joining  cells  in  this  method  is 
equivalent  to  increasing  the  sectional  area  of 
the  plates  which  diminishes  internal  resistance. 
This  is  the  arrangement  for  obtaining  quan- 
tity. 

Requisites  of  a  Good  Battery:  The  ideal 
battery  should  have  (1)  high  and  constant 
electromotive  force,  (2)  low  internal  resist- 
ance, (3)  constant  current  flow  without  polar- 
ization and  (4)  no  local  action. 

The  use  of  a  battery  for  the  production  of 
current  to  be  utilized  as  the  inducing  current 
of  an  induction  coil  is  fraught  with  much 
trouble,  many  trials  and  much  disappointment. 
It  is  only  where  electric  mains  are  not  avail- 
able that  they  find  their  field  of  usefulness. 

Storage  Batteries,  Secondary  Cells  or  Ac- 
cumulators: The  products  of  electrolysis  have 


a  tendency  to  reunite  by  virtue  of  the  chemical 
affinity  existing  between  them  and  in  this  pro- 
cess there  is  produced  an  electric  curffent  with 
an  electromotive  force  smaller  or  equal  to  that 
causing  electrolysis  but  in  the  opposite  direc- 
tion. 

If  the  current  of  a  voltaic  cell  be  passed  by 
means  of  two  similar  electrodes,  as  platinum 
through  a  solution  of  sulphuric  acid  the  water 
will  be  decomposed  into  O  and  H,  the  former 
appearing  at  the  positive  and  the  latter  at  the 
negative.  When  the  current  ceases  to  flow 
through  the  acid  the  oxygen  and  hj'drogen 
will  reunite  with  the  production  of  water  and 
an  electric  current  will  be  generated  which  in 
this  particular  instance  will  have  an  electro- 
motive force  equal  to  the  original.  It  is  thus 
seen  that  the  electric  energy  of  chemical  de- 
composition is  recovered  by  chemical  recompo- 
sition,  and  upon  this  principle  the  storage  bat- 
teries are  constructed.  These  accumulators  do 
not  store  electricity,  only  energy.  The  accum- 
ulators commonly  used  are  of  the  lead  elec- 
trode type.  The  passage  of  a  current  by  means 
of  two  lead  electrodes  immersed  in  a  solution 
of  sulphuric  acid  spc.  gr.  1200  at  60°  F.  (1-5) 
by  electrolysis  liberates  oxygen  at  the  anode 
and  hydrogen  at  the  cathode.  The  oxygen 
combines  with  the  lead  of  the  positive  plate  to 
form  lead  peroxide,  a  reddish  brown  deposit, 
while  the  cathode  becomes  coated  with  lead 
sulphate  or  spongy  lead.  To  charge  fully, 
the  passing  of  the  current  is  continued  until 
there  is  evolution  of  free  oxygen  and  hydrogen 
showing  that  the  saturation  point  has  been 
reached,  chemical  action  upon  the  plates  hav- 
ing ceased.  This  usually  takes  place  when 
a  voltage  of  2.5  per  cell  is  obtained. 

The  battery  is  now  said  to  be  charged  and 
the  potential  energy  of  the  chemical  separa- 
tion will  remain  in  this  state  for  days  if  the 
circuit  remains  open.  When  the  circuit  is 
closed,  however,  a  reversed  current  results  and 
the  peroxide  is  resolved  into  oxide  on  the  posi- 
tive and  from  the  sulphate  to  the  oxide  on  the 
negative,  and  this  continues  until  the  plates  are 
chemically  identical,  when  the  flow  of  current 
ceases.     The  battery  may  thus  be  repeatedly 


EFFECTS  OF  ELECTRICITY 


charged.  The  accumulator  has  been  modi- 
fied by  giving  the  lead  plates  a  preliminary 
coating  of  red  lead.  To  facilitate  the  chemical 
changes  some  forms  of  accumulators  have  one 
of  the  plates  grooved  with  a  layer  of  lead 
oxide  pressed  into  the  plate.  In  the  most 
modern  types  red  lead  made  into  a  paste  with 
sulphuric  acid  is  pressed  into  the  holes  of  a 
leaden  grid. 

TItc  Edison  Accinnnlator  or  Storage  Bat- 
tery: In  this  type  of  storage  battery,  lead  is 
not  utilized.  The  containing  vessel  is  of  steel. 
The  positive  pole  is  a  grid  of  steel,  nickel- 
plated,  supporting  closely  packed  vertical  rows 
of  perforated  steel  tubes,  made  by  rolling  steel 
strips  into  a  long  spiral.  These  are  filled  with 
alternate  layers  of  metallic  nickel  and  of  nickel 
hydrate.  The  negative  grids  are  also  of  steel 
and  contain  oxide  of  iron.  The  electrolyte  is 
a  twenty-one  per  cent  solution  of  potassium 
hydrate.  The  plates  do  not  buckle  or  bend 
and  the  cell  does  not  deteriorate  if  left  im- 
charged.  Its  e.  m.  f.  is  low,  about  1.3  per 
cell.  The  cells  may  be  connected  in  series 
or  in  parallel.  For  use  with  an  induction  coil 
20  cells  with  a  tension  of  two  volts  each  are 
necessary.  At  best  when  charged  they  only 
yield  about  80%  of  the  energy  transmitted  to 
them. 

Though  only  used  in  exceptional  cases,  stor- 
age cells  are  of  great  value  in  those  localities 
where  no  other  current  source  is  available. 

The  capacity  of  a  storage  battery  is  usually 
expressed  in  "ampere  hours,"  implying  the 
product  of  maximum  discharging  current  by 
the  length  of  time  in  hours  it  discharges.  The 
capacity  will  be  slightly  reduced  when  an  ac- 
cumulator discharges  for  a  very  short  length 
of  time  at  a  higher  rate  than  the  maximum 
discharge  current.  If  we  assume  that  a  certain 
accumulator  has  a  capacity  of  forty-eight 
ampere  hours  at  the  maximum  discharge  of 
eight  hours,  then  we  may  use  the  battery 
normally  at  one  charge  as  follows : 

With  one  ampere  for  48  hours 

With  two  amperes  for  24  hours 

With  four  amperes  for  12  hours 

With  eight  amperes  for  6  hours 


It  must  not  l)e  forgotten  that  the  cells  should 
be  arranged  in  "series." 

The  utmost  precautions  must  be  taken  in 
caring  for  storage  batteries  because  they  are 
very  sensitive  to  shocks  and  any  bending  of 
the  plates  is  likely  to  give  rise  to  short  cir- 
cuits. There  is  likewise  danger  of  leakage  of 
acid,  breaking  of  glass  cells,  etc.  The  cells 
must  be  frequently  charged  and  discharged ;  if 
this  is  neglected  the  plates  will  rapidly  be- 
come impaired. 

In  subsequent  charges  and  in  general  use, 
it  is  only  necessary  to  charge  until  the  voltage 
is  2.5  per  cell  while  charging. 

When  discharging,  the  electromotive  force 
of  each  cell  as  measured  by  the  voltmeter, 
must  not  be  allowed  to  sink  below  1.85  volts; 
thus,  in  the  case  of  a  6-cell  battery  11  volts  is 
the  lowest  limit  for  the  discharge.  They 
should  never  be  overdischarged,  more  always 
being  put  in  them  than  taken  out. 

Cells  should  never  be  permitted  to  stand  idle 
if  more  than  75  per  cent,  of  their  capacity  has 
been  used.  Whether  or  not  used,  they  should 
have  a  period  of  charging  every  three  weeks, 
and  should  be  regularly  charged  and  dis- 
charged. 

The  plates  should  be  well  covered  with  the 
electrolyte.  If  the  latter  has  been  spilt  or  be- 
come partly  evaporated,  it  must  be  replaced 
with  distilled  water.  During  the  charging  the 
top  should  be  open  so  as  to  allow  the  escape 
of  the  hydrogen  bubbles.  Unnecessary  vibra- 
tion and  shaking  of  the  cells  should  be  avoided. 
^^'ith  proper  care  the  storage  battery  should 
render  good  service. 

Storage  batteries  may  be  charged  in  any  of 
the  following  four  ways :  ( 1 )  by  primary 
cells,    (2)    by  the   110  volt    (direct)    current, 

(3)  by  the   rectified  alternating  current   and 

(4)  by  a  mechanical  dynamo. 

EFFECTS   OF  ELECTRICITY 

Electricity  is  capable  of  producing  the  fol- 
lowing efifects :  (1)  physiological,  (2)  thermic, 
(3)  luminous,  (4)  chemical,  (5)  magnetic, 
(6)  inductive  and  {7 )  mechanical. 


10 


MAGNETISM 


Physiological:  The  electric  current  has  the 
power  of  causing  protoplasm  to  contract.  A 
muscle  will  contract  both  upon  the  make  or 
the  break  of  the  current  sent  through  it. 
Rapidly  interrupting  the  current  throws  it  into 
a  tetanic  spasm. 

Thermic:  The  quantity  of  heat  produced 
in  a  conductor  by  the  passage  of  an  electric 
current  is  proportional  to  the  resistance 
of  the  conductor  and  the  square  of  the 
current  strength.  The  greater  the  resist- 
ance the  more  heat  will  be  produced  with  the 
same  current.  A  thin  wire  having  great  resist- 
ance may  be  heated  to  incandescence.  Resist- 
ance in  a  circuit  produces  heat  at  the  expense 
of  electrical  energy.  This  principle  is  utilized 
in  the  construction  of  the  electric  light  and 
galvano-cautery.  This  phenomenon  is  of  con- 
siderable value  in  insuring  the  safety  of  elec- 
tric installations  by  preventing  the  entrance  of 
too  strong  a  current  into  the  circuit,  as  might 
happen  when  the  current  finds  a  shorter  path 
through  contact  between  certain  parts  of  a 
circuit,  the  accident  being  called  short-circuit- 
ing. Short  pieces  of  lead  wire  or  tape  called 
fuses  of  such  structure  that  a  certain  current 
strength  will  melt  them  are  interposed  along 
the  circuit.  AA'hen  the  current  exceeds  that 
strength,  they  are  melted  and  break  the  cir- 
cuit. 

Liimiiioiis:  \\'hen  the  two  charged  termin- 
als are  brought  together  or  separated  sparks 
are  seen.  This  spark  at  the  site  of  the  inter- 
ruption of  the  current  is  due  to  a  change  of 
resistance  at  this  point,  which  induces  a  cur- 
rent of  high  electromotive  force  in  the  circuit, 
thus  causing  a  spark  to  fly  across  the  air  space 
separating  the  poles  of  the  conductor  where 
the  continuity  is  broken.  The  brilliant  light 
of  the  carbon  lamp  is  obtained  by  sending  a 
current  of  considerable  strength  through  two 
pointed  rods  of  carbon  which  are  kept  in  con- 
tact with  each  other  until  incandescent  and 
then  slightly  separated,  thus  constituting  the 
electric  arc.  The  color  of  the  spark  depends 
on  the  electromotive  force,  and  the  nature  of 
the   terminals   and   the    surrounding   medium. 

Chemical:     Either  chemical  combination  or 


decomposition  may  be  produced  by  the  electric 
current.  The  decomposition  of  substances  by 
the  current  is  called  electrolysis.  The«£om- 
pound  decomposed,  which  must  be  in  fluid  con- 
dition and  a  conductor,  is  called  an  electro- 
lyte. The  electrode  immersed  in  the  solution 
which  is  connected  with  the  negative  pole  of 
the  battery  is  the  cathode,  while  the  other  is 
the  anode.  The  current  enters  through  the 
cathode  and  leaves  through  the  anode.  The 
products  of  decomposition  are  ions.  If  the 
current  be  passed  through  sulphuric  acid 
hydrogen  ions  are  developed  at  the  cathode 
and  oxygen  ions  at  the  anode. 

Magnetic,  Inductive  and  Mechanical:  These 
effects  are  considered  under  magnetism. 

MAGNETISM 
Magnets     are     substances     which     possess 
the     property     of     attracting     certain     sub- 


FiG.  2 — Plan  view  of  the  held  of  force  between  the 
two  poles  of  a  magnet  fixed  with  iron  filings 
and  plaster  of  paris   (Johnson) 

Stances  and  of  assuming  a  particular  position 
when  freely  suspended, — north  and  south. 
This  power  of  attraction  is  not  evenly  dis- 
tributed throughout  the  magnet  but  is  greatest 
at  or  near  the  ends.  These  points  of  greatest 
attraction  are  called  the  poles  of  the  magnet. 
The  middle  of  the  magnet  has  no  attractive 
power  and  is  called  the  equator  or  neutral 
point.  The  pole  which  points  to  the  north 
when  the  magnet  is  freely  suspended  is  called 
the  north  pole  or  the  positive,  while  the  other 
is  the  south  or  negative  pole.  The  like  poles 
of  two  magnets  will  repel  while  the  opposite 
poles  will  attract  each  other. 


PRODUCTION  OF  E.  AF.  F.  I'.V  ELECTRO-AIAGNETIC  INDUCTJOX 


11 


There  are  four  kinds  of  magnets: 
Natural — Loadstone      or      inagnelic      oxide 
of    iron    Fe.,0_,    whicJT    retains    its    magnetism 
permanently. 

Artificial — A.  Magnets  by  contact — are 
made  by  rubbing  iron  or  steel  against  a  mag- 
net. Those  made  from  iron  are  temporary 
while  those  made  from  steel  retain  their  mag- 
netism. 

B.  IMagnets  by  induction — magnetism  de- 
veloped in  iron  or  steel  by  a  magnet  without 
actual  contact  of  the  two. 

C.  Magnets  by  electricity  or  electro-mag- 
nets. Magnetism  developed  in  iron  or  steel 
by  passing  an  electric  current  about  it. 

Those  substances  as  iron,  steel,  and  nickel 
which  magnets  are  capable  of  attracting  are 
called  magnetic  substances.  Those  substances 
which  magnets  repel,  bismuth,  zinc,  and  cop- 
per are  called  diamagnetic  substances.  There 
are  also  substances  which  are  neutral  to  mag- 
netic influence  as  glass  and  paper.  The  induc- 
tive action  of  a  magnet  can  only  be  cut  of?  by 
a  magnetic  substance.  Magnetic  substances 
should  not  be  confused  with  magnets.  Iron 
is  the  most  magnetic  substance  known.  The 
force  with  which  a  magnet  attracts  or  repels 
another  magnet  or  any  piece  of  iron  and  steel 
is  called  magnetic  force  or  strength. 


Fig.  2(7. — Profile  of  the  field  of  force  between  the 
two  poles  of  a  magnet  (Johnson).  The  profile 
of  the  field  of  force  between  two  poles  of  a 
magnet,  fixed  with  iron  filings  and  plaster  of 
Paris.  The  iron  filing  in  the  plaster  of  Paris 
was  made  into  a  paste  with  water  and  was  sifted 
over  the  field  area  through  a  medium  mesh 
sieve.  The  hardening  of  the  mixture  gave  a 
relief  map  or  a  three  dimension  model  of  the 
field  of  force. 


The  laws  of  magnetic  force  are :  (  1  )  that 
like  poles  repel  and  unlike  poles  attract  one 
another.  (2)  The  force  exerted  between  2 
magnetic  poles  varies  inversely  as  the  square 
of  the  distance  between  them. 

The  region  about  a  magnet  within  which  it 
exerts  its  magnetic  force  is  called  its  magnetic 


field.  If  iron  filings  are  scattered  upon  a 
paper  under  which  there  has  been  placed  a 
bar  magnet,  the  particles  arrange  themselves 
in  thread-like  curves  which  diverge  from  one 
pole  to  meet  at  the  other.  These  lines  of  iron 
particles  indicate  the  direction  of  the  magnetic 
influence  and  are  called  lines  of  magnetic  force 
or  of  magnetic  induction  and  it  is  along  these 
lines  that  magnetic  induction  takes  place.  The 
filings  in  these  curves  have  become  temporary 
magnets  through  induction  and  have  arranged 
themselves  with  opposite  poles  adjoining. 

The  complete  path  taken  by  the  lines  of  force 
within  and  without  the  magnet  comprises  the 
magnetic  circuit  of  that  magnet.  The  lines 
of  force  may  then  be  considered  as  a  flux  or 
stream  moving  around  the  magnetic  circuit, 
though  there  is  really  no  flow.  The  equiva- 
lent to  resistance  in  an  electric  circuit  is  styled 
reluctance  in  a  magnetic  circuit. 

A  ring  magnet  has  neither  poles  nor  ex- 
ternal magnetic  field.  So,  too,  when  four  bar 
magnets  are  arranged  to  form  a  rectangle, 
there  is  no  field  outside  of  the  iron  composing 
the  magnets.  This  institutes  a  closed  mag- 
netic field,  and  as  such  has  no  magnetic  leak- 
age. In  the  construction  of  transformers  it 
is  desirable  that  there  be  little  or  no  external 
field. 

If  a  section  be  cut  from  a  ring  magnet,  two 
powerful  poles  are  formed.  Such  a  form  of 
magnetic  circuit  is  utilized  as  permanent  mag- 
nets in  the  construction  of  generators  or  mo- 
tors. A  piece  of  soft  iron  placed  across  the 
poles  of  a  horseshoe  magnet  is  called  an  arma- 
ture. 

The  Production  of  Electro-Motive  Force 
by  Electro-Magnetic  Induction.  By  induction 
is  meant  the  influence  an  electrified  body  ex- 
erts upon  a  neighboring  unelectrified  body,  or 
that  which  a  magnetized  body  exerts  upon  a 
neighboring  magnetic  but  unmagnetized  bodv. 
An  induced  current  is  a  current  produced  in 
a  conductor  by  the  influence  of  a  neighboring 
current  or  magnet.  The  current  used  to  pro- 
duce this  eft'ect  is  called  the  inducing  current. 
An  e.  m.  f.  is  induced  in  any  conductor  that 
cuts  across  or  is  cut  bv  a  magnetic  flux.    This 


12 


INDUCED  CURRENT 


may  be  done  either  by  pushing  the  conductor 
through  the  hues  or  by  moving  the  flux  so 
that  the  hnes  cut  through  the  conductor. 

Electro-Magnet.  A  conductor  through 
which  a  vohaic  current  is  passing  is  a  tem- 
porary magnet.  This  magnetic  effect  is  in- 
creased if  the  wire  be  insulated  and  wound 
in  a  coil.  Such  a  coil  is  called  a  helix 
or  solenoid  and  while  the  current  is  passing 
through  it  has  a  north  and  south  pole  and  a 
distinct  magnetic  field  exactly  like  a  bar  mag- 
net. The  lines  of  force  about  a  wire  through 
which  the  current  is  flowing  are  in  the  shape 
of  concentric  circles. 

Thus,  a  current  of  electrons  in  motion  pro- 
duces magnetism. 

The  more  windings  the  solenoid  has  within 
one  centimeter  and  the  larger  the  current 
which  flows  through  it,  the  more  powerful  the 
magnetic  field. 

If,  while  the  current  is  passing  through 
the  helix,  a  bar  of  soft  iron  is  introduced  into 
the  coil,  the  bar  of  iron,  or  core,  as  it  is  called, 
being  in  the  magnetic  field  of  the  helix,  will 
become  a  magnet.  This  process  is  reversible ; 
that  is  to  say,  a  flux  of  magnetism  will  gen- 
erate e.  m.  f.  in  a  closed  circuit.  This  com- 
bination of  helix  and  core  has  greater  mag- 
netic power  than  the  helix  alone  and  consti- 
tutes an  electro-magnet.  Electro-magnets  are 
utilized  in  all  generators. 

Induced  Current  may  be  produced  in  four 
ways : 

1.  Stationary  flux  and  moving  conductor. 

Example — A  circuit  is  moved  between  the 
poles  of  a  magnet,  permanent  or  electro. 
Direct  current  generators  and  motors  are 
built  on  this  principle. 

2.  Moving  flux  and  stationary  conductor. 

Example — The  insertion  or  withdrawal 
of  an  electro  or  permanent  magnet  into  and 
from  a  solenoid. 

Inductive  Action  of  a  Permanent  Magnet. 
It  was  discovered  by  Farady  in  1831  that  if 
a  magnet  either  permanent  or  of  the  electro- 
magnetic type  was  thrust  near  or  into  or  away 
from  a  helix  of  wire  a  current  will  appear  in 


the  helix.  This  current  will  show  itself  in 
the  wire  of  the  helix  just  as  long  as  the  mag- 
net is  kept  moving  in  or  out  of  the*" helix. 
The  current  induced  in  the  helix  by  the  mag- 
net during  its  introduction  will  be  in  the 
opposite  direction  to  that  induced  during  its 
withdrawal.  Whenever  therefore  either  the 
helix  or  magnet  is  moved,  the  lines  of  force  of 
the  magnet  are  cut  by  the  helix. 

The  e.  m.  f.  induced  is  proportional  to  the 
number  of  turns  in  the  solenoid.  Alternating 
current  generators  and  synchronous  motors 
are  built  on  the  principle  of  a  moving  flux 
cutting  a  stationary  conductor  for  they  have 
stationary  armatures  and  rotating  fields.  The 
e.  m.  f.  of  the  current  induced  in  the  helix  de- 
pends on  the  rate  at  which  the  lines  of  force 
are  cut,  and  is  proportional  to  the  strength  of 
the  magnet  and  the  rapidity  of  its  movements. 

3.  Stationary   Conductor  and   Variable   Flux. 
Example — Strengthening    or    weakening 
the   magnetic   motive    force   of   an   electro- 
magnet. 

This  is  equivalent  to  making  and  breaking 
the  current  in  the  primary  of  an  induction 
coil  or  to  the  effect  of  alternating  current 
in  the  primary  of  a  closed  core  transformer. 
If  within  or  near  a  solenoid  connected  to  a 
galvanometer,  there  be  placed,  instead  of  a 
magnet,  another  smaller  coil  or  solenoid  of  in- 
sulated copper  wire  the  two  coils  being  thor- 
oughlv  insulated  from  each  other,  at  the  instant 
the  current  is  sent  through  the  primary  coil,  it 
induces  a  current  in  the  secondary  coil  as 
shown  by  the  deflection  of  the  galvanometer 
needle,  and  at  the  instant  the  current  is  cut  off 
from  the  primary  coil  another  current  is  in- 
duced in  the  secondary  as  again  shown  by  the 
deflection  of  the  galvanometer  which  this  time 
deviates  to  the  opposite  direction,  thus  proving 
that  both  at  the  make  and  at  the  break  of  the 
current  in  the  primary  coil  a  current  is  induced 
in  the  secondary,  but  the  direction  of  the  in- 
duced current  at  the  make  is  opposite  to  the 
induced  current  of  the  break.  This  is  called 
mutual  induction  between  two  concentric  coils. 


GENERATORS 


13 


Both  currents  are  only  momentary  in  dura- 
tion. A  current  flowing  steadily  and  continu- 
ously without  change  of  phase  through  the  pri- 
mary coil  has  no  inducing  effect.  It  is  only  at 
the  instant  of  its  alteration  that  the  inductive 
phenomena  occur.  The  inductive  effect  is  here 
explained  on  the  theory  that  the  conductors  in 
the  secondary  cut  the  lines  of  force  set  up  by 
the  primary  on  account  of  a  variation  in  the 
value  of  the  magnetic  field.  If  instead  of  open- 
ing and  closing  the  circuit  (making  and  break- 
ing the  current),  it  is  rapidly  strengthened, 
weakened  and  reversed  the  same  inductive 
effects  will  be  manifested  in  the  secondary 
coil. 

Inductive  Action  of  a  Temporary  Magnet: 
If  within  the  helix  in  circuit  with  a  galvano- 
meter there  be  placed  a  bundle  of  soft  iron 
wires  and  the  end  of  a  permanent  magnet  be 
brought  near  the  ends  of  the  iron  wires  a 
strong  induced  current  will  appear  in  the 
helix  deflecting  the  galvanometer  needle.  As 
the  magnet  is  withdrawn  from  the  region  of 
the  wires,  a  current  will  reappear  which  will 
flow  in  the  opposite  direction  to  the  first  in- 
duced current.  In  these  effects  the  induced 
e.  m.  f.  results  from  varying  the  reluctance 
of  the  magnetic  circuits. 
4.      Variable    flux    and    a   moving   conductor. 

Example. — Moving  a  conductor  across 
the  lines  of  force  generated  by  a  solenoid 
through  which  a  variable  current  is  flowing. 

Two  e.  m.  f.'s  are  induced,  one  by  the 
movement  of  the  conductor  and  another  by 
the  variable  flux.  The  e.  m.  f.  induced  in  the 
conductor  will  be  the  sum  of  the  two. 

Self-induction.  A  change  of  current  in  a 
conductor  induces  e.  m.  f.  in  the  conductor 
itself.  The  e.  m.  f.  produced  flows  in  the 
opposite  direction  and  is  called  counter 
e.  m.  f.  of  said  induction. 

Just  as  the  primary  solenoid  or  coil  acts 
as  a  whole  upon  the  secondary  so  the  indi- 
vidual turns  or  convolutions  of  wire  of  the 
primary  act  inductively  upon  the  other  spiral 
windings  or  convolutions  as  if  they  were 
separate  circuits.     This  is  known  as  self  in- 


duction and  the  current  thus  produced  as  the 
extra-current. 

At  the  make  of  the  current  in  the  pri- 
mary the  extra  current  induced  in  the  wind- 
ings of  the  primary  has  a  direction  which 
is  opposite  to  the  inducing  or  main  cur- 
rent, against  which  it  acts  (counter  e.  m.  f.) 
and  prevents  an  expression  of  its  maximum 
intensity.  The  secondary  output  may  thus  be 
weakened  by  augmenting  the  self-induction  in 
the  primary  circuit.  The  self-induction  may 
be  increased  by  connecting  the  primary  wind- 
ings in  series.  \\'hen  connected  in  parallel, 
the  self-induction  is  diminished.  The  extra 
current  at  the  breaking  of  the  primary  circuit 
has  the  same  direction  as  the  main  current 
and  increases  its  effect  upon  the  secondary. 
Current  flowing  through  the  primary  cir- 
cuit is  therefore  due  to  the  resultant  of  the 
voltage  applied  to  the  primary  minus  that  of 
the  self  induced  current.  This  explains  why 
the  current  flowing  through  the  primary  cir- 
cuit of  a  transformer  is  high  when  the  avail- 
able counter  electro-motive  force  is  not  used, 
resistance  being  always  so  low  that  it  may  be 
disregarded.  A  choke  coil  makes  use  of  this 
principle.  The  counter  electro-motive  force 
is  regulated  by  moving  the  core  into  or  out 
of  a  coil  of  wire.  With  the  core  out  there  is 
no  opposition  to  the  current  except  resistance, 
which  is  low.  \\'ith  the  core  in,  the  counter 
e.  m.  f.  may  nearly  equal  the  impressed  volt- 
age. 

Electric  Generators — Dynamos — Production 
of  Currents:  It  has  already  been  indicated 
that  a  dynamo  does  not  generate  electricity 
any  more  than  a  pinnp  generates  water.  A 
generator  is  a  device  by  which  electricity  al- 
ready in  existence  is  forced  to  n^ove  and 
transmit  energy,  operate  motors,  energize 
lamps,  etc.  Stated  in  simple  terms,  a  dynamo 
may  be  said  to  be  a  machine  to  move  a  coil 
of  wire  near  the  ends  of  a  magnet. 

By  mechanically  rotating  a  portion  of  the 
generator  the  conductor  parts  of  it  will  cut 
or  be  cut  by  a  magnetic  flux  (the  latter  being 
produced  by  electro  magnets),  and  thus  there 
will  be  induced  in  the  conductors  an  e.  m.  f. 


14 


DYNAMOS 


If  this  e.  m.  f.  be  impressed  on  a  closed  circuit 
it  will  force  through  it  an  electric  current.  In 
commercial  generators  strong  electro  magnets 
are  used  to  produce  the  fields  and  the  con- 
ductors are  moved  through  the  fields  at  high 
speed  to  generate  the  e.  m.  f .  The  high  speed 
(high  rate  of  cutting  of  lines)  is  attained  by 
rotating  conductors  formed  into  loops,  through 
magnetic  fields.  Transformers  as  well  as  gen- 
erators are  also  constructed  according  to  the 
principles  of  induction  above  outlined,  but 
whereas  the  generator  cuts  the  lines  of  force 
by  mechanical  motion,  in  the  transformers  the 
lines  of  force  are  cut  by  magnetization  and 
demagnetization,  in  other  words  by  changes 
in  current  intensity  which  by  causing  an  ex- 
pansion and  a  contraction  of  the  flux  of  the 
lines  of  force  permit  the  latter  to  cut  any 
conductor  within  their  range. 

The  value  of  the  e.  m.  f.  or  voltage  induced 
is  determined  by  the  number  of  lines  of  force 
cut  in  a  second  and  this  depends  on : 

1.  The  speed  with  which  the  conductor 
moves  through  the  flux  or  the  flux  moves 
through  the  conductor.     The  faster  this  move- 


FiG.  3. — Diagram  of  alternating  current  generator 
(alternator).  By  rotation  of  the  coil  in  a  lon- 
gitudinal axis  between  the  poles  of  a  magnet, 
the  current  is  induced  and  delivered  by  the  coil 
to  the  circuit  extending  from  the  slip  rings. 
The  arrows  indicate  the  direction  of  the  flow 
of  current.  The  slip  rings  alternately  become 
positive  and  negative  at  each  half  turn. 

ment   the    greater   the    number    of    lines    cut, 
therefore,  the  greater  the  e.  m.  f. 

2.  Strength  of  the  field  through  which  the 
conductor  cuts.  A  greater  e.  m.  f.  will  be  pro- 
duced in  a  strong  field  than  in  a  weak  one. 

3.  Angle  of  direction  of  the  conductor  with 


respect  to  direction  of  field.  It  will  cut 
through  more  lines  of  force  when  moving 
through  them  at  right  angles  in  a  specified 
time  than  otherwise. 

4.  Length  of  conductor  which  cuts  lines. 
The  longer  the  conductor  the  greater  the 
e.  m.  f.  induced. 

If  a  closed  circuit  is  rotated  between  the 
poles  of  a  magnet,  one  complete  cycle  of  an 
alternating  current  is  produced  for  each  revo- 
lution. This  is  the  essential  principle  of  a 
dynamo.  When  this  wire  loop  is  rapidly  re- 
volved between  the  poles  of  a  magnet  a  current 
will  be  induced  in  the  loop  which  will  flow  in 
one  direction  as  it  approaches  the  vertical  posi- 
tion and  in  the  opposite  direction  as  it  ap- 
proaches the  horizontal.  If  the  ends  of  the 
loop  are  connected  to  two  metallic  rings,  the 
current  may  be  collected  by  two  brushes  made 
to  rest  on  them.  (Fig.  3).  A  galvanometer 
connected  to  the  brushes  will  show  a  deflection 
of  the  needle  first  in  one  direction  and  then  in 
the  other  indicating  a  current  of  the  alternating 
type.  This  is  the  principle  of  construction  of 
the  alternating  current  dynamo. 

If  the  ends  of  the  loop  are  connected,  one 


Fig.  4. — Diagram  of  the  elements  of  a  direct  current 
generator.  The  slip  rings  have  been  replaced 
by  a  split  tube.  The  two  halves  of  the  tube  are 
separated  from  each  other  by  an  air  space. 
This  split  tube  serves  to  unite  the  reverse  im- 
pulses and  turn  successive  current  waves  in  one 
direction.  It  is  called  a  commutator.  In  the 
simple  arrangement,  the  e.  m.  f.  falls  to  zero 
twice  in  each  revolution.  In  practice  the  coils 
are  connected  and  numerous  and  symmetrically 
grouped  so  that  some  of  them  are  always  active. 

to  either  half  of  a  split  tube  the  halves  being 
separated  by  an  air  space,  a  diff'erent  kind  of 
current    will    be    found    flowing    through    the 


MOTORS 


15 


external  circuit  of  the  galvanometer.  The  mere 
use  of  the  split  tube  instead  of  the  rings  so 
alters  conditions  that  there  is  now  generated  a 
direct  current,  one  which  travels  always  in 
the  same  direction.  (  Fig.  4. )  This  is  the  prin- 
ciple of  construction  of  the  direct  current 
dvnamo.  The  split  ring  is  therefore  called 
a  commutator.  \\'hat  the  commutator  does 
is  to  collect  akcays  on  one  brush  the  current 
made  by  the  coil  cutting  the  lines  in  one  direc- 
tion, and  on  the  other  brush  always  the  current 
made  by  the  coil  cutting  the  lines  in  the  reverse 
direction.  The  fixed  magnet  is  called  the  field 
magnet  and  the  revolving  loop  which  in  the 
dynamo  is  a  rotating  system  of  coils,  is  called 
the  armature.  The  rings  in  the  alternating 
current  type  of  machine  to  which  the  coils  are 
connected  are  called  slip  rings.  In  the  direct 
current  machine  the  armature  coils  extend 
from  one  commutator  segment  to  another 
placed  directly  opposite  to  the  first.  The 
dynamo  is  therefore  a  device  for  converting 
mechanical  into  electrical  energy. 

When  the  dynamos  are  connected  in  par- 
allel or  multiple — there  is  a  greater  amount  and 
flow  of  current  but  no  increase  of  potential. 
Where  both  great  potential  and  great  quan- 
tity are  desired,  a  combination  of  the  two 
methods  of  connection  is  used.  In  the  same 
way  as  the  potential  or  amperage  depends  on 
the  nature  of  the  elements  and  the  electrolyte, 
so  the  characteristics  of  a  dynamo  depend  on 
the  size  and  shape  of  its  electro-magnets, 
the  size  and  quantity  of  wire  in  the  armature 
and  the  speed  at  which  the  armature  is  made  to 
revolve. 

Motors. — An  electric  motor  is  an  electro- 
magnetic machine  in  which  mechanical  power 
is  derived  from  electric  currents,  electrical 
energy  being  turned  back  into  mechanical 
power.  The  action  of  the  electric  motor  is 
the  simple  converse  of  that  of  the  dynamo. 

There  are  two  kinds  of  motors,  those  used 
with  the  continuous  currents  and  those  used 
with  the  alternating  currents.  Their  construc- 
tion is  similar  to  that  of  the  dynamo.  In  the 
motor  the  passing  of  electric  current  in  the  ar- 
mature     reacts        -on      the      field      magnets 


resulting  in  the  arnialurc  being  inilled 
around  in  a  turning  motion  (torque).  The 
two  factors  of  this  mechanical  rotary  power 
are  torque  and  speed,  the  former  being  pro- 
portional to  the  current  and  the  latter  to  the 


Fig.  5. — Commutator  and  brushes.  The  brushes,  con- 
sisting of  blocks  of  graphite,  carbon  or  copper 
strips,  clamped  in  suitable  holders,  press  against 
the  commutator,  which  consists  of  copper  bars, 
insulated  from  each  other  and  connected  to  the 
junction  annature  coils  which  are  so  joined  as 
to  make  the  coil  endless. 


voltage.  Since  for  x-ray  work  it  is  important 
that  the  speed  of  the  motor  be  maintained  at 
all  loads,  a  compound  wound  motor  of  ample 
capacit}'  should  be  used. 

If  an  e.  m.  f.  of  220  volts  is  impressed  across 
the  terminals  of  a  d.  c.  motor  and  the  current 
terminals  of  a  d.  c.  motor  and  the  current 
through  the  motor  is  80  amperes,  the  motor 
consumes  6600  watts  or  6.6  K^^'.  or  8.8  h.  p. 

Electric  Current 

An  electric  circuit  is  the  total  path  traveled 
by  the  current :  it  includes  the  source,  the  re- 
ceptive device  in  which  useful  work  is  per- 
formed and  the  conductors  connecting  the 
two,  together  with  any  switches  or  devices  for 
inaking  or  breaking  the  circuit  or  interrupting 
the  flow  of  current. 

The  circuit  is  closed  when  the  current  can 
flow  and  open  or  broken  when  one  or  more 
breaks  in  the  continuitv  of  the  circuit  nrevents 


16 


CURRENTS 


its  flow,  ^^'hen  a  part  of  the  circuit  is  in  con- 
tact with  the  earth  or  with  a  conductor  con- 
nected to  the  earth  it  is  grounded.  A  source 
of  e.  m.  f.  is  short  circuited  when  its  termi- 
nals are  connected  by  a  conducting  part  of 
very  low  resistance. 

A  synchronous  motor  makes  either  the  same 
or  a  multiple  of  the  number  of  revolutions  per 
minute  of  the  generator  supplying  it.  With  a  60 
cycle  a.c.  there  would  be  7200  alternations  per 
minute.  Since  one  alternation  is  produced  each 
time  a  conductor  passes  a  pole  of  the  generator 
the  speed  of  a  four  pole  motor  with  a  60  cycle 


Currents. —  TIic  properties  of  electric  cur- 
rents are: 

1.  The  transmission  of  power.  "^ 

2.  The  magnetization  of  iron  and  steel. 

3.  The  creation  of  magnetic  fields. 

4.  The  generation  of  induced  currents. 

5.  The  production  of  heat  in  conductors  of 
high  resistance. 

6.  The  transference  of  metal  by  electro- 
chemical action. 

An  alternating  current  is  one  which  flows, 
first  in  one  direction  and  then  in  the  opposite 
in  regular  succession.  The  current  starts  at 
zero  value  (see  Fig.  6),  increases  in  strength 


^ 

^ 

i 

5 

s 

i 

— 

i^yft 

^. 

= 

n; 

P 

— 

:zi 

^ 

■ 

•0 

°1 

1 

i 

-^ 

-&• 

1        0 

i          a 

^"t 

:^i_  1  in.^ 

S 

i 

B 

1 

^ 

—  • 

= 

1 

>      • 

— 

w 

•       «e 

r^ 

-^ 

r^ 

■      N 

7^- 

N 

r— 

>^ 

^s^ 

-^ 

7^ 

Fig.  5a. — Alternating  Current.    25  Cycle. 

^ 

^          ..          a.         •.         . 

J.,^.y 

' 

s 

^ 

Fig.  5if. — Direct  Pulsating  Current. 


Fig.   5^^ — Oscillating    Current. 


.,                  C.                0,.               0*               0..                ..               0.^                0«               0,                 ,0                 H                  ,.                   1 

e 

-t 

Fig.    5r. — Continuous    Direct    Current. 


\ 

' 

■ 

.    . 

,    , 

*«-« 

7          0 

T          ' 

.     . 

' 





i 

— 1 

Fig.  5c. — Alternating  Current.     60  Cycle. 


Fig.  5/. — Direct  Constant  Current. 


in  a  positive  direction  above  the  axial  line  until 
current  would  have  to  be  1800  revolutions  per  it  reaches  the  maximum  (P),  then  falls  to 
minute  if  synchronism    is    to    be    maintained,      zero   value    (S),   after   which   it   rises   to    its 


Lou-^o/roae. 
Genera  rof^ 


^T*^ 


/i^-vo/faae  Trirj^fniU'on  Lmc~  ^ 


Lpu-vo/fiiy€. 


^ecoridaiy  Winding 


Ternary  l^o&ir. 


lou-^o/t,i 


?maiy  l^in^inaS.-  '  ■      ■■  ' 

Fig.  5p. — Illustrating  the  Transmission  of  Currents 


(^     (^     (^     (^  ^(^ 


DIRECT  CURRENTS 


17 


maximum  negative  value  below  the  axial  line 
and  falls  again  to  zero.  This  process  is  re- 
peated in  a  periodic  manner. 

A  direct  current  is  a  current  which  though 
it  may  vary  in  its  rate  of  flow  always  flows  in 
the  same  direction. 


Fig.  6. — Diagram  of  alternating  electromotive-force 
sine  wave-form 

A  dii-ect  current  may  be  continuous  or  pul- 
sating or  constant.  A  pulsating  current  is  a 
continuous  current  which  varies  regularly.  A 
constant  current  is  one  which  continues  in  its 
flow  for  some  time  with  unvarying  strength. 
It  may  be  either  direct  or  alternating.  An 
alternating  current  is  one  which  reverses  its 
direction  at  regular  intervals. 

The  time  is  measured  horizontally  from  left 
to  right  on  the  horizontal  OX.     The  strength 


A            B          5.           ^          3          <^_ 

A 1 A  p  A  /  \  A  / 

*           3           C 

\  A  ;\    \ 

i'A  y  V  V  y 

V  V  y 

Fig.  /. — Current  curve  of  a  three  phase  system. 
Three  successive  alternating  currents,  a,  b,  c,  are 
outlined.  When  one  is  at  its  positive  maximum 
value,  the  other  two  are  each  at  negative  half 
value.  When  any  one  is  at  zero  value,  the 
other  two  are  at  86.6  of  the  maximum,  one  pos- 
itive and  the  other  negative. 

and  direction  of  the  current  at  any  part  are 
indicated  by  the  length  of  the  vertical   ordi- 


nates  and  their  positions  relative  to  the  base 
line.  The  total  horizontal  line  OX  measures 
only  a  fraction  of  a  second.  Each  succeeding 
positive   half   wave   is   exactly  similar  to  the 


Fig.  8. — The  curves  OT  represent  the  current  flow- 
ing in  a  given  circuit.  OR  represents  the  alter- 
nating e.  m.  f.  in  the  circuit.  The  periodicity 
of  these  two  quantities  is  the  same  and  they 
are  also  in  phase.  But  the  curve  LX  which 
represents  another  e.  m.  f.  lags  behind  OR  and 
there  is  therefore  a  difference  in  phase  between 
them  equal  to  ^  of  a  period. 


preceding  one  and  the  same  similarity  exists 
between  the  negative  half  waves.  The  cur- 
rent rises  and  falls  through  a  certain  repeated 
cycle  of  values.     The  time   required   for  the 


Motor 


Fig.  g. — Scheme  of  a  three  wire  system,  sometimes 
called  Edison  three  wire  system.  Two  generators 
alike  in  voltage  and  capacity  are  connected  in 
series  between  the  outside  wires.  The  neutral  wire 
is  in  the  circuit  between  the  two  machines,  thus 
the  voltage  between  the  two  outside  wires  is 
double  that  between  either  outside  and  neutral 
wire,  no  volt  lamps  are  connected  between 
either  outside  and  neutral  wire.  If  an  equal 
number  is  connected  at  each  side,  there  is  no 
current  flow  in  the  neutral.  The  system  is  bal- 
anced. The  220  volt  motor  is  connected  to  the 
two  outer  leads. 


18 


PROPERTIES   OF  ALTERXATIXG  CURRENTS 


performance  of  one  complete  cycle  is  called 
the  periodic  time.  This  is  represented  by  the 
distance  along  the  horizontal  line  OT,  Fig.  6. 
The  frequency  of  an  alternating  current  is  the 
number  of  complete  cycles  performed  in  one 
second. 

Generally  the  number  of  cycles  per  second 
is  between  25  and  100  and  in  the  vast  majority 
of  cases  60.  In  the  latter  the  number  of  al- 
ternations is  120.  As  shown  in  Fig.  6,  since  the 
negative  half  wave  is  generally  similar  in  shape 
and  equal  in  magnitude  to  the  positive  half 
wave,  it  therefore  follows  that  the  ordinate 
PK  above  the  axis  and  PK  below  the  axis 
are  equal  in  length.  To  get  the  mean  value 
of  an  alternating  current  or  e.  m.  f.  it  is  neces- 
sary to  take  the  average  of  any  ordinates  of 
the  wave  diagram  or  to  measure  the  area  of 
the  curve  OPS  and  divide  it  by  the  length  OS. 
which  usually  equals  .707  of  the  maximum 
value.  Two  alternating  e.  m.  f.'s  of  the  same 
character  and  periodicity  or  an  alternating  cur- 
rent and  the  e.  m.  f.  to  which  it  owes  its  exist- 
ence are  said  to  be  in  phase  when  the  growth, 
decrease,  reversal,  and  maximum  value  occur 


simultaneously,  OTS  and  ORS.  (Fig.  8.)  A 
suitably  constructed  generator  may  give  an  al- 
ternating current  in  which  the  waves  haiK  such 
a  phase  variation  that  they  begin  and  end  a 
fraction  of  a  period  behind  each  other.  (Fig. 
7.)  In  other  words,  their  zero  and  niaximum 
values  are  the  same  but  not  reached  at  the 
same  moment.  There  are  thus  single  phase, 
double  phase,  and  triple  or  polyphase  alternat- 
ing currents. 

By  means  of  a  commutator,  the  negative 
lower  half  of  the  wave  of  an  alternating  cur- 
rent may  be  turned  in  the  same  direction  as 
the  positive  half,  or  upper  wave,  shown  sche- 
matically in  Fig.  11. 

The  strength  of  the  current  still  increases 
from  zero  to  maximum  twice  during  one 
period  but  the  two  waves  now  have  the  same 
direction.  By  a  certain  arrangement  several 
waves  of  varying  phases  may  be  produced  in 
a  period  and  if  a  sufficient  number,  at  least 
twelve,  are  produced,  a  current  which  does 
not  vary  to  any  considerable  degree  is  the  re- 
sult— a  rapidly  pulsating  and  practically  a  di- 
rect current :  shown  schematicallv  in  Fig.  II. 


WIRING  TABLE 


Amperes 


Distance  in  Feet  (One  Way)  Producing  a  Drop  of  1  Volt  for  Given  Currents  and  Given  Sizes  of  Wire 


10 


15 


20 


25 


30 


35 


40 


45 


50 


60 


80 


90 


100 


3 

ho 

3 

ca 
O 


Cfl 


18 
16 
14 
12 
10 

8 

6 

5 

4 

3 

2 

1 

0 

00 
000 
0000 


75.2 

120.0 

190.0 

302.0 

480.0 

764.0 

1,215.0 

1,533.0 

1,933.0 

2,437.0 

3,073.0 


15. 

24. 

38 

60 

96 

153 

243 

307 

387 

487 

615 

774 

978 

1,232 


12,0 

19.0 

30.2 

48.0 

76.4 

121.5 

153.3 

193.0 

244.0 

307.0 

774.0'387.0 


489 .0 
616.0 
777.0 
980.0 


12 

20 '. 

32. 

51. 

81 
102 
129 
162 
205 
258 
326 
410 
518 
653 


9. 

15. 

24. 

38. 

60. 

76. 

96. 
122. 
154. 
194. 
245. 
308 
388 
490 


7. 

12. 

19. 

30. 

48. 

61. 

77. 

97. 
123 
155 
195 
246 
311 
392 


10. 

16. 

25. 

40. 

51. 

64 

81. 
102. 
129 
163 
205 
259 
01326 


13 

21 

34. 

43. 

55 

69 

87 

111 

140 

176 

222 

280 


12 

19 

30 

38 

48 

60 

76 

96 

122 

154 

194 

245 


10. 

17- 

27. 

34. 

43 

54. 

68 

86 

109 

137 

173 


0218.0 


15. 

2/i. 

30. 

38. 

48. 

61. 

77. 

97. 
123 
155 
196 


12. 

20 

25 

32 

40 

51 

64 

81 

102 

129 

163 


17.4 
21.9 
27.6 
34.8 
43.9 
55,3 
69.9 
88.0 
111,0 
140.0 


15 
19 
24 
30 
38 
48 
61. 
77. 
97. 
122. 


17.0 
21.5 
27 
34 
43.0 
54  3 
68.4 
86.3 
108.9 


15.3 
19.3 
24.4 
30.7 
38.7 
48.9 
61.6 
77.7 
98.0 


T--\BLE  I 


RECTIFICATION  OF  ALTERNATING  CURRENTS 


19 


The  direct  current  is  generally  indicated 
by  a  straight  line.  As  a  rule  the  direct  current 
is  supplied  from  a  three  wire  system,  and  gen- 
erated by  two  similar  dynamos  connected  in 
series.  This  makes  both  a  current  of  110  and 
220  volts,  d.  c,  available  depending  upon 
whether  an  inner  and  outer  lead,  or  both  outer 
leads  are  used. 

In  alternating  current  supply  the  three  wire 
system  is  also  utilized  in  making  either  220 
a.  c.  or  110  a.  c.  available. 

In  arranging  for  standard  installations  it  is 
well  to  provide  a  circuit  of  sufficient  capacity 
to  carry  from  75  to  100  amperes  without  over- 
loading, overheating  or  drop  in  voltage.  The 
line  drop  at  the  highest  current  should  not 
exceed  3  per  cent. 

If  essential  the  low-tension,  alternating 
current  may  be  changed  into  the  direct.  This 
is  done  by ; 

1.  A  rotary  converter. 

2.  A  mercury  vapor  lamp  rectifier. 

3.  Chemical  rectifiers. 


Fig.  10. — Diagram  of  a  simple  converter.  Such  an 
apparatus  is  necessary  for  converting  alternat- 
ing currents  into  direct.  In  the  above  diagram 
the  rotary  converter  has  both  the  simple  com- 
mutator to  collect  the  continuous  current  and 
a  pair  of  slip  rings  for  the  alternating  current. 
It  may  act  as  a  motor  if  supplied  by  either  cur- 
rent or  if  driven  mechanically,  which  may  gen- 
erate both  currents  at  the  same  time.  The  ar- 
matures are  wound  like  a  continuous  current 
dynamo  but  there  is  provided  at  either  end  of 
the  shaft  two  or  more  slip  rings,  connected  to 
suitable  points  on  the  winding. 

1.  For  rectification  of  an  alternating  current 
by  means  of  a  rotary,  the  motor  must  be  de- 
signed for  the  frequency  of  the  current. 
The  rotary  converters  have  armatures  wound 
exactly  like  those  of  a  continuous  current  dy- 
namo but  at  the  other  end  of  the  shaft  are 


slip  rings.  Supplied  with  alternating  current 
the  machine  operates  as  a  synchronous  motor, 
the  continuous  current  being  drawn  from  the 
brushes  at  the  commutator. 

2.  The  Cooper-Hewitt  mercury  arc  lamp 
rectifies,  but  at  considerable  cost  of  current. 
Lodge  has  described  a  mercury  arc  rec- 
tifier, which  has  an  iron  anode  and  a  mercury 
cathode.  This  has  an  electro-magnetic  ring 
which  is  used  to  deflect  the  cathode  stream,  but 
allows  the  anode  particles  free  play. 

3.  These  consist  of  cells  with  electrodes 
of  aluminum  and  iron,  in  an  electrolvte  cota- 


FiG.  II. — The  commutation  of  the  alternating  wave 
as  schematically  shown  in  the  first  line  is  indi- 
cated in  the  second  and  its  further  transforma- 
tion into  what  is  a  direct  pulsating  current  in 
the  lower  lines,  is  possible  by  an  increase  in  the 
number  of  windings,  the  machine  being  made 
to  give  two  or  more  electro-motive  forces  of 
equal  amplitude  but  slightly  differing  in  phase, 
either  one-third  of  the  period  or  one-sixth  of 
the  period  behind  each  other.  This,  when  com- 
mutated.  gives  the  diagrammatic  appearance  of 
a  direct  current. 

posed  of  a  solution  of  sodium  bicarbonate  and 
distilled  water. 

Their  action  depends  on  the  property 
which  aluminum  possesses  of  high  resistance 
to  the  passage  of  current,  becoming  covered 
with  a  layer  of  aluminum  hydroxide  by  elec- 
trolysis, when  the  current  flows  from  the  iron 
electrode  to  the  aluminum.  A  battery  of  such 
cells  is  necessary  for  rectification.  This  method 
has  manv  disadvantages.  The  efiiciency  of 
the  cells  is  less  than  "S^f  and  they  require 
constant  cooling. 

j\Ie.\surixg  Ix.stru.mexts 
The  electrical   measuring  instruments   used 
in  practical  roentgenology  are  the  voltmeter, 
ammeter,  milliammeter  and  the  kilovoltmeter. 


20 


METERS 


When  a  current  of  electricity  is  passed 
through  a  conductor  such  as  an  insulated 
wire,  the  space  surrounding  the  conductor 
is  a  magnetic  field.  The  insulated  wire 
itself  becomes  a  temporary  magnet  when  cur- 
rent is  passing  through  it.  An  electric  current 
flowing  parallel  with  or  spirally  about  a  mag- 
netic needle  will  deflect  it  from  its  position  of 
north  and  south  in  proportion  to  the  intensity 


Fig.  12. — E-xternal  circuit  of  a  voltaic  element.  The 
space  surrounding  the  wire  is  a  magnetic  field. 
Between  A  and  B  the  wire  has  been  curved  into 
a  spiral. 

of  the  current.  This  property  of  a  magnetic 
needle  is  utilized  for  the  determination  of  the 
presence  of  an  electric  current,  its  direction 
and  strength.  A  magnetic  needle  employed 
in  this  way  is  called  a  galvanometer.  If  the 
galvanometer  is  calibrated  so  that  it  may  be 
read  directly  in  amperes  it  is  called  an  am- 
meter. 

An  especially  constructed  galvanometer  may 
be  provided  with  a  scale  to  indicate  the  num- 
ber of  volts  between  its  terminals  and  is  called 
a  volt  meter. 


Fig.  13. — A  bar  of  soft  iron  inserted  into  the  spiral 
of  the  circuit.  The  stronger  the  current  the 
further  into  the  spiral  or  solenoid  the  bar  will 
be  drawn.  An  index  attached  to  this  bar  will 
indicate  on  a  scale  the  relative  strength  of  the 
current  in  amperes,  flowing  through  the  circuit 
providing  the  solenoid  does  not  itself  offer  any 
particular  resistance.  This  is  the  principle  of 
construction  of  one  type  of  amperemeter.  The 
ideal  ammeter  should  have  no  appreciable  resis- 
tance. 
S — indicates  the  source. 


Fig.  14. — In  practice,  therefore,  the  amperemeter 
is  connected  in  series  in  the  circuit  because  it 
measures  the  current  flowing  through.  In  the 
diagram  the  instrument  replaces  the  spiral. 

M— indicates  the  location  of  the  load.  S — indicates 
the  source. 


METERS 


21 


M 


+ 


Fig.  15. — External  circuit  of  a  voltaic  element  nito 
which  a  shunt  circuit-  has  been  introduced  be- 
tween R  and  S.  If  the  size,  length  and  material 
through  RS  is  the  same  as  AB,  the  current  and 
voltage  will  be  the  same.  But  if  the  wire  RS 
offers  greater  resistance,  then  this  parallel  cir- 
cuit will  pass  less  current,  though  the  voltage 
will  be  the  same.  This  is  the  principle  of  con- 
struction of  the  voltmeter.  The  ideal  voltmeter 
should   have  infinite  resistance. 


Fic.  16. — In  practise,  therefore,  the  voltmeter  is 
connected  across  the  line  in  parallel.  In  the 
diagram  the  instrument  replaces  the  shunt  cir- 
cuit. The  resistance  of  the  amperemeter  is 
negligible. 
M — indicates  the  location  of  a  load. 


In  construction  of  volt  and  amperemeter, 
the  properties  of  a  current  or  charge,  by  which 
it  produces  motion  of  a  conductor  are  used. 
Some  of  these  means  are : 

1.  Soft  iron  moving  in  a  magnetic  field. 

2.  A  coil  moving  in  a  magnetic  field. 

3.  Electrostatic  attraction  between  a  mov- 
able and  a  fixed  conductor. 

4.  Expansion  of  a  fine  coil  by  heating  effects 
of  a  current. 

The  ammeter  measures  the  current  strength 
in  amperes,  that  is  to  say,  the  rate  of 
flow,  and  is  made  with  a  short  coil  of  very 
low  resistance,  to  avoid  any  alteration  in 
the  strength  of  the  current  flowing  through 
it.     A  voltmeter  is  a  high  resistance  galvano- 


Fig.   17. — Soft  iron  amperemeter. 

meter  with  a  scale  graduated  to  give  the  num- 
ber of  Z'olfs  difference  in  potential  between 
its  terminals.  It  is  really  a  galvanometer  with- 
a  coil  of  very  long  thin  wire  of  high  resistance, 
often  several  thousand  ohms.  \'ery  little  cur- 
rent will  flow  through  the  coil.  The  current 
that  does  flow  is  proportional  to  the  potential 
dift'erence  applied  to  the  two  ends  of  the  cir- 
cuit afl:'ecting  the  galvanometer  needle  by 
moving  it  over  a  scale  graduated  in  volts. 
It  is  important  to  remember  that  a  volt- 
meter does  not  measure  electricity  but  only 
the  pressure  which  tries  to  pass  a  charge  be- 
tween two  regions. 

Meters. — 1.  Soft  iron  instruments.  (Fig.  17. )• 
A  small  piece  of  roft  iron  (I)  carrying  a  poin- 


22 


METERS 


ter  is  pivoted  inside  a  small  coil  (c)  so  that  when 
the  current  passes  around  the  coil,  the  iron  is 
sucked  into  the  coil  to  a  variable  extent,  de- 
pending on  the  strength  of  the  current  and 
registers  on  the  dial  in  amperes. 

2.  Moving  coil  instruments.     (Figs.  18  and 


Fig.    i8. — Moving    coil    voltmeter.      Instruments    of 
this  type  are  suited   for   direct  current. 


19.)  The  polar  space  of  a  steel  horse-shoe 
magnet  provided  with  soft  iron  pole-pieces, 
contains  a  cylindrical  core  of  soft  iron.  A 
small  coil  (c)  carr}-ing  a  pointer  (p)  is  pivoted 


Fig.    19. — Aloving   coil   voltmeter. 

to  move  freely  in  the  narrow  annular  gap  be- 
tween the  pole  pieces  and  the  iron  core.  Its 
motion  is  controlled  by  two  springs  (s)  simi- 
lar to  watch  springs,  one  above  and  below.  A 
large,  non-inductive  resistance  is  connected 
in  series  with  the  coil,  if  the  instrument  is 
to  be  used  as  a  voltmeter.     (Fig.  21.) 


But  if  it  is  to  be  an  ammeter,  the  coil  is 
shunted  with  a  conductor  of  very  low  re- 
sistance to  carry  the  largest  current  wi^out 
undue  heating.      (Fig.  20.) 

3.  Electro-static  instruments.  This  type  of 
instrument  is  used  only  as  a  voltmeter  for 
which  purpose  it  is  ideally  suited  and  its  action 
depends  upon  the  repulsion  between  two 
charged  surfaces. 


Fig.  20. — Ammeter.  D  is  a  conductor  of  low  resist- 
ance though  the  current  flows  in  parallel  to  the 
circuit  R  disposed  about  the  core.  M — Arma- 
ture of   magnet. 

4.  Hot-wire  instruments.  The  principle  of 
these  instruments  is  expansion  of  a  long,  thin 
wire  of  high  resistance  ( usually  a  platinum 
silver  alloy)  when  connected  across  a  circuit. 
The  movement  of  a  pointer  over  a  scale  by 
the  increase  in  length  of  the  heated  wire  indi- 
cates   with    accuracy    the    voltage    (direct    or 


Fig.  21. — Voltmeter.  Sp.  is  the  non-inductive  resis- 
tance in  series  with  coil  and  core  placed  between 
armature. 

alternating ) .  Ammeters  have  the  hot  wire  in 
parallel  with  a  suitable  shunt.  The  heating 
ettect  is  proportional  to  the  square  of  the  cur- 
rent or  voltage.  The  millimeter  is  an  am- 
meter graduated  to  record  milliamperes  and  is 
placed  in  series  in  the  high-tension  circuit 
(secondary). 


CHAPTER  II 
■  INDUCTION  APPARATUS— OPEN 
CORE— COIL— INTERRUPTERS 

As  will  be  seen  later  the  energization  of  an 
x-ray  tube  requires  high  voltage  because  of 
the  resistance  offered  by  the  vacuum. 

Such  tubes  can  only  be  energized  by  cur- 
rents varying  from  1  to  200  milliamperes  and 
at  voltages  varying  from  25,000  to  100,000. 

This  energy  is  obtained  by  the  use  of  induc- 
tion or  transformer  apparatus  constructed  ac- 
cording to  the  principles  of  electro-magnetic 
induction. 

By  means  of  electro-magnetic  induction,  cur- 
rents of  comparatively  low  e.  m.  f.  are  trans- 
formed  into   currents   of    high   e.    ni.    f.,   and 


Fig.  22. — Upon  an  iron  ring  Faraday  wound  two  iso- 
lated coils  of  wire.  One  coil  was  connected  to 
a  battery  and  the  other  to  a  galvanometer.  He 
found  that  whenever  the  current  was  turned  on 
or  off  in  the  coil,  secondary  currents  were  in- 
duced in  the  opposite  coil,  as  shown  by  the  de- 
flection of  the  galvanometer.  The  current  in  one 
coil  magnetizes  the  iron  ring  and  the  magnetic 
lines  created  by  it  pass  through  the  secondary 
circuit,  setting  up  induced  current.  This  ring 
with  its  two  coils  wound  on  a  closed  iron  cir- 
cuit is  the  prototype  of  the  transformer  and  in- 
duction coil. 


vice  versa.  If  the  energizing  current  is  applied 
to  the  short  coil,  the  inducing  effect  on  the 
secondary  is  in  an  increase  of  e.  m.  f.,  thus 
constituting  a  step-up  transformer.  If  the 
inducing  current  is  applied  to  the  long  coil, 
the  inducing  effect  on  the  short  coil  is  a 
diminution  of  the  e.  m.  .f.,  thus  constituting  a 
step-down  transformer. 

With     the     direct     current     the     transfor- 
mation is  accomplished  by  a  periodic  interrup- 


ter and  an  induction  apparatus.  With  the  al- 
ternating current  it  may  be  done  without  the 
agency  of  an  interrupter. 

In  a  general  way  it  may  be  stated  that  the 
three  principal  parts  of  a  transformer  are : 

1.  The  iron  core  to  provide  a  circuit  of  low 
reluctance  for  the  magnetic  flux. 

2.  The  primary  winding  to  which  the 
energy  is  applied. 

3.  The  secondary  winding  in  which  the 
energy  is  induced  and  which  delivers  it  to  the 
secondary  circuit. 

It  is  the  form,  shape  and  relationship  which 
the  primary  bears  to  the  secondary  and  the 
form  and  method  of  application  of  the  ener- 
gizing current  which  gives  the  various  kinds 
of  transformation. 

If  the  primary  is  to  utilize  all  the  magnetic 
lines  of  force  and  minimize  magnetic  leakage 
or  loss,  the  primary  core  is  made  in  rectangular 
or  triangular  form,  thus  constituting  a  so- 
called  "closed-core,"  and  the  transforming  ap- 
paratus to  which  it  belongs  is  a  closed-core 
transformer.  If,  on  the  other  hand,  the  pri- 
mary core  is  a  single  bundle,  so  that  only  a 
part  of  the  magnetic  lines  of  force  are  utilized, 
and  there  is,  therefore,  considerable  magnetic 
leakage  or  loss,  the  primary  is  of  the  open- 
core  variety  and  the  transformer  is  of  the 
open-core  variety. 

Induction  Coil. 

This  may  be  considered  as  a  transformer 
with  an  open  magnetic  circuit  energized  bv  a 
pulsating  direct  current. 

The  induction  coil  consists  of  three  main 
parts : 

The  core. 

The  primary  winding. 

The  secondary  winding. 

The  core  and  primary  winding  are  some- 
times designated  under  one  name,  the  primary. 

Core :  The  core  consists  of  a  bundle  of  soft 
iron  wires  (a  b)  carefully  annealed  to  facilitate 
the  magnetic  changes  which  take  place  in  them. 
Such  a  core  of  soft  iron  wire  rods  is  preferable 


23 


24 


INDUCTION  COIL 


to  a  bar  of  soft  iron,  because  it  is  less  easily 
heated.  But  a  core  of  varnished  soft  iron  plates, 
having  a  high  resistive  index,  is  the  most  effi- 
cient of  all.  The  core  is  enclosed  within  a 
hollow  cylinder  of  some  insulating  material 
of  rubber  or  fiber. 

Primary  Winding:  Upon  this  insulating 
tube  there  is  wound  the  primary  winding  con- 
sisting of  one  or  several  layers  of  insulated 
copper  wire  (gh)  of  sufficient  coarseness  to  be 
able  to  carry  heavy  currents  without  heating. 
The  ends  of  this  wire  terminate  in  contacts  at 
the  side,  for  connection  with  the  primary  or 
inducing  current.     (  Fig.  23. ) 

This  primary  winding  may  consist  of  a 
single  strand  of  coarse  wire  wound  from  one 
end  of  the  core  to  the  other  and  then  back, 
the  two  layers  being  separated  by  some  insu- 
lating material.  There  may  also  be  several 
separate  strands  of  wire  wound  in  this  man- 
ner, one  over  the  other,  each  layer  being  insu- 
lated from  the  other  and  each  strand  term- 
inating  in   a    separate   terminal.      A   primary 


Fig.  23. — Plan   of  construction  of  a   coil.     Ab — pri- 
mary   (open   core),   gh — primary   winding,   cd — 
insulating  material,  ef — secondary  terminals. 
(Gocht) 

of  the  latter  construction  is  called  a  variable 
induction  primary.  It  is  possible  with  such 
a  primary  to  vary  the  induction  for  tubes  of 
different  vacua,  by  using  either  a  single  wind- 
ing or  connecting  the  various  windings  serially 
or  in  parallel.  By  using  the  windings  serially 
the  self-induction  is  greatly  increased  and  the 
true  induction  thereby  inhibited,  thus  making 
it  applicable  for  the  energizing  of  a  tube  of 
low  vacuum.  The  self  induction  is  minimized 
when  the  windings  are  connected  in  parallel 
but   the   maximum   inductive    eft'ects    are    ob- 


tained, for  the  production  of  rays  in  a  tube  of 
high  vacuum.* 

The  primary  windings  are  thorougljly  and 
entirely  covered  by  an  insulating  sheath  (c) 
usually  made  of  mica  (which  gives  best  ser- 
vice), rubber  or  gutta  percha  or  porcelain. 
The  primary  may  be  stationary  or  removable, 
so  as  to  permit  the  substitution  of  another  of 
different  winding,  when  necessary. 

Secondary  Winding :  Upon  the  tube  (d)  in- 
sulating the  primary  is  wound  the  secondary, 
which  consists  of  a  considerable  length  of  fine 
insulated  copper  wire.  This  is  wound  in  sym- 
metrical layers,  each  one  being  carefully  in- 
sulated from  the  other  by  a  sheet  of  waxed 
paper  or  gutta  percha  tissue.  Because  of  its 
length,  every  precaution  must  be  taken  to 
thoroughly  insulate  the  secondary  winding, 
which,  if  defective,  would  allow  discharges  be- 
tween the  various  windings,  which,  causing 
fusing  of  the  wires,  would  completely  destroy 
the  efiiciency  of  the  apparatus.  The  secondary 
is  enclosed  within  a  rubber  or  wooden  box  and 
then  the  insulation  is  further  strengthened 
by  thorough  impregnation  with  wax,  paraf- 
fine  or  petroleum  jelly.  In  the  modern  coils, 
the  secondary  is  wound  in  several  sections, 
each  section  insulated  from  the  other  with  a 
mica  or  glass  disc.  The  insulation  may  thus 
be  perfected  and  any  break-down  within  the 
secondary  winding  easily  detected  and  re- 
paired. Winding  in  sections  relieves  the  strain, 
which  must  exist  between  the  wire  of  the 
secondary  and  the  electric  strain  on  the  pri- 
mary tube. 

The  secondary  windings  end  in  two  binding 
posts,  (e.  f.)  one  usually  bearing  a  disc  and  the 
other  a  pointed  rod,  and  it  is  between  these  two 
terminals  that  the  induced  current  makes  itself 
manifest  as  a  discharge  or  spark.  Coils  are 
designated  by  this  sparking  distance,  a  twelve 
inch  coil  being  one  whose  secondary  terminals 
are  twelve  inches  apart,  this  being  in  the  par- 
ticular coil  the  longest  distance  the  discharge 
of  induced  electricity  is  capable  of  bridging. 

*  This  holds  true  for  the  Wehnelt  interrupter. 
With  the  mercury  the  variable  inductance  is  unnec- 
essaryr. 


INDUCTION  COIL 


25 


The  sparking  distance  of  a  coil  is  no  criterion 
of  its  efficiency  or  its  capacity.  The  capacity 
depends  on  several  factors : 

1.  The  number  of  turns  and  size  of  wire 
of  the  secondary  spool. 

2.  The  strength  of  the  magnetic  field. 

3.  The  suddenness  of  the  magnetic  changes. 
The  aim  at  the  present  time  is  to  construct 

coils  having  sparking  lengths  of  ten  to  twelve 
inches,  but  capable  of  delivering  heavy  sec- 
ondary currents  with  a  minimum  amount  of 
inverse. 

Because  the  primary  and  secondary  coils  are 
both  wound  on  the  same  core,  the  induced 
voltage  is  directly  proportional  to  the  number 
of  turns  of  wire  in  either  coil.  If  the  primary 
winding  consists  of  fifty  turns  of  wire  of  any 
series  and  the  secondary  of  a  thousand  turns, 
the    ratio    of    transformations    is     1    to    20. 

If  the  turn  of  the  wire  of  the  secondary  is 
twice  that  of  the  primary  the  voltage  of  the 
secondary  will  be  twice  that  of  the  primary. 
On  the  other  hand,  if  the  secondary  has  only 
one-fiftieth  as  many  turns  as  the  primary,  the 
secondary  current  will  be  only  one-fiftieth  of 
the  voltage  of  the  primary. 

There  is  a  certain  amount  of  loss  due  to  the 
ohmic  resistance  of  the  wire  and  magnetic 
leakage,  less  in  closed-core  transformers  than 
in  open  core. 

The  principles  of  transformation  may  be 
thus  used  not  only  for  the  purpose  of  stepping 
up  of  the  current  to  a  higher  potential  but  also 
for  a  stepping  down  of  the  current  to  a  lower 
potential.  With  this  change  in  the  voltage 
there  is  a  change  also  in  the  amperage,  that  is 
to  say,  where  the  volts  increase,  as  in  a  step- 
up  transformer,  the  amperage  falls.  On  the 
other  hand  in  the  step-down  transformer, 
where  the  voltage  diminishes,  the  amperage 
increases. 

Method  of  Action  of  the  Induction  Coil :  At 
the  instant  the  current  is  switched  into  the 
primary  winding,  according  to  the  principle 
of  electro-magnetic  induction  considered,  the 
iron  wire  core  will  become  a  temporary  mag- 
net and  the  core   and '  winding  together   will 


then  constitute  an  electro-magnet,  which  will 
act  in  a  powerful  inductive  manner  upon  the 
secondary  winding,  giving  rise  to  an  induced 
current  which  will  be  of  higher  electromotive 
force,  though  of  less  amperage  than  the  main 
inducing,  current.  Again  at  the  instant  the 
current  ceases  to  flow  in  the  primary  winding 
(break),  the  same  inductive  phenomenon  will 
occur. 

In  considering  electro-magnetic  induction  it 
was  stated  that  a  beginning,  approaching,  and 
increasing  inducing  current  will  give  rise  to 
an  inverse  induced  current,  while  an  ending, 
withdrawing  and  diminishing  inducing  current 
will  give  rise  to  a  direct  induced  current. 
This  direct  induced  current  should  have  a 
higher  e.  m.  f.  than  the  inverse  induced  cur- 
rent. 

What  is  particularly  desired  for  the  pro- 
duction of  the  Roentgen  ray  in  a  vacuum 
tube  is  this  direct,  induced  current.  The  in- 
verse induced  current  is  an  impulse  in  the 
wrong  direction  and  not  only  is  it  unneces- 
sary for  the  production  of  the  ray.  but  being 
permitted  to  enter  the  tube,  has  a  tendency 
to  rapidly  raise  its  vacuum  and  to  produce 
inverse  and  secondary  rays,  making  the  tube 
useless   for   radiographic   work. 

It  is,  therefore,  the  aim  to  either  weaken  or, 
if  possible,  to  entirely  abolish  this  inverse 
phase  of  induction  and  this  may  be  accom- 
plished as  follows : 

1.  By  a  large  number  of  turns  in  the  pri- 
mary winding. 

2.  By  effectively  breaking  the  primary,  in- 
ducing current. 

The  greater  the  frequency  with  which  the 
current  is  made  and  broken,  the  greater  the 
tension  of  the  induction  effect,  so  that  it  is 
apparent  that  to  obtain  the  maximum  induc- 
tion eff'ects  from  the  induction  coil,  it  is  neces- 
sary that  the  primary  current  be  interrupted 
regularly,  sharply,  rapidly  and  completely. 
Various  devices  have,  from  time  to  time,  been 
used  for  the  purpose  of  interrupting  the  pri- 
mary current :  but  in  the  primitive  method 
of  Fitzeau  the  manual  manipulation  of  a 
coarse    file,    and    in    the    present    electrolytic 


26 


INTERRUPTERS 


method  of  Wehnelt,  and  in  the  rotary  mercury 
interrupters,  the  aim  sought  has  always  been 
the  same. 

Condensers 

When  the  interruptions  of  the  primary  cur- 
rent are  relatively  slow  as  in  a  mechanical  in- 
terrupter, or  in  some  types  of  mercury-jet 
breaks,  it  becomes  necessary  to  use  some  form 
of  condenser  in  order  to  prevent  inverse.  A 
condenser  is  an  electrical  apparatus  which 
stores  up  much  electricity  on  a  small  surface. 
This  condenser  consists  of  thin  layers  of  tin 
foil,  insulated  from  each  other  by  waxed  paper 
or  mica  and  so  connected  that  its  capacity  may 
be  varied  by  utilizing  a  greater  or  less  portion 
of  the  condensing  surfaces.  This  tuning  of 
the  capacity  of  the  condenser  to  the  induc- 
tance of  the  coil  and  the  variety  of  break  is 
very  necessary  if  the  maximum  inductive  ef- 
fects are  to  be  obtained. 

Alternate  sheets  of  foil  are  connected  to 
each  other  and  the  two  leads  extend  one  to 
either  side  of  the  primary  circuit.  With  the 
condenser  in  the  circuit  the  first  rush  of  cur- 
rent is  taken  up  by  it  and  the  magnetization 
of  the  core  grows  slowly,  a  much-desired 
effect,  but  at  the  break  the  condenser  rapidly 
discharges  through  the  primary  circuit  and 
quick  demagnetization  of  the  core  takes  place. 
All  this  tends  to  strengthen  and  accentuate  the 
induced  current  at  the  break,  which  is  in  the 
proper  direction  and  desirable,  and  to  minimize 
the  current  induced  at  the  make,  which  is  "  in- 
verse "  and  undesirable.  It  also  tends  to  mini- 
mize the  self-induction  in  the  primary  of  the 
coil  whose  effects  are  visibly  shown  in  the 
primary  circuit  by  sparking  at  the  interrupter 
contacts.  With  the  coil  working  in  unison 
with  the  interrupter  with  a  high  number  of 
breaking  current  impulses  per  second  in  a  cur- 
rent of  sufficient  tension  and  intensity,  the  con- 
denser becomes  unnecessary,  as  in  the  electro- 
lytic interrupters. 

INTERRUPTERS 

In  order  to  obtain  the  maximum  inductive 
effects  in  a  coil  the  primary  interruptions  must 
be  rapid,  regular  and  short. 


If  a  current  of  30  amperes  is  reduced  to  0 
in  .03  seconds,  the  current  has  changed  at  the 
rate  of  1000  amperes  per  second.  If  it  re- 
quires .06  seconds  to  do  this,  the  change  takes 
place  at  the  rate  of  500  amperes  per  second. 
The  secondary  voltage  has  therefore  only  half 
the  value  under  the  latter  conditions. 

There  are  three  varieties  of  interrupters : 

1.  Mechanical. 

2.  Mercury. 

3.  Electrolytic. 


Fig.  24. — Plan  of  a  winding  of  coil  and  connection 
to   condenser   and   mechanical   break. 

MECHANICAL   INTERRUPTER.      (Figs. 
24,  25.) 

Parts : 

1.  Core  of  primary  of  coil.     (A) 

2.  Hammer,  which  consists  of  a  metal  strip,  act- 

ing   as    a    spring,    to    which    is    fastened    a 
piece  of  soft  iron.     (B) 

3.  Contacts,   consisting  of   two   platinum   points, 

one  fastened  to  spring   (C)    and  one  to  an 
adjustable   screw   horizontally  placed.      (D) 

The  hammer  is  so  placed  that  the  soft  iron 
is  just  opposite  the  core.  The  spring  holds 
the  platintim  tips  in  contact.  One  end  of  the 
circuit  is  attached  to  the  adjttstable  screw,  the 
other  end  extends  to  the  primary  of  the  coil. 
The  current  flows  through  the  adjustable 
screw,  through  the  platinum  points,  held  in 
contact  by  the  spring,  into  the  primary  of  the 
coil.  The  iron  core  becomes  magnetic  and 
draws  the  piece  of  soft  iron  to  itself,  separat- 
ing the  platinum  contacts  and  interrtipting  the 


MECHANICAL  INTERRUPTER 


27 


current,  which  results  in  the  demagnetization 
of  the  core.  The  spring  is  then  released  and  the 
end  of  the  platinum  points  again  come  in  con- 
tact and  the  circuit  is  made.  This  may  be 
repeated  depending  on  the  mechanical  pattern 
from  thirty  to  two  hundred  and  sixty  times 
per    second. 

Mechanical  interrupters  may  be  constructed 
to  carry  heavy  currents  and  give  a  high  rate 
of  interruptions  according  to  the  principle  as 
above  described.  The  interrupter  action  takes 
place  however  in  an  accessory  small  coil  or 
independent  electro-magnet,  specially  wound, 
and  it  is  only  the  interrupted  primary,  which 
is  carried  to  the  core  of  the   induction  coil. 


Fic.  25. — Mechanical  break,  activated  b\-  a  winding- 
less  motor. 

The  contacts  in  such  interrupters  should  have 
large  faces  placed  parallel,  and  be  of  platinum 
or  tungsten. 

In  one  modern  form  of  mechanical  break 
the  contact  points  are  activated  by  a  winding- 
less  motor,  which  causes  the  make  and  break 
by  an  eccentric  acting  on  one  of  the  contacts. 
The  motor  is  driven  by  the  make  and  break 
of  the  magnetic  field,  produced  in  a  coil  which 
is  connected  across  the'  break  gap.     The  fre- 


quency of  interruptions  is  easily  controllable. 
The  interrupter  may  be  used  either  with  direct 
or  alternating  current  and  draws  from  five  to 
seven  amperes.  It  gives  a  discharge  fairly  free 
from  inverse.  It  is  an  excellent  form  for  pro- 
longed use  with  small  currents,  as  in  fluoro- 
scopy. 

MERCURY  INTERRUPTERS 

In  this  type  the  current  is  interrupted  be- 
tween   electrodes — a    moving    or    stationarv 


M 


Fig.  26. — Jet  type  of  centrifugal  mercurj'  interrup- 
ter.     (Morton.) 

column  of  mercury  and  a  moving  or  station- 
ary strip  of  metal.  There  are  two  general 
types:  The  "Dip"  and  the  "Centrifugal." 
Because  of  electrical  action  taking  place  in 
them,  a  non-conductor,  oil,  alcohol,  acetone, 
ether  or  coal-gas,  is  placed  over  the  mercur}' 
to  prevent  o.xidation.  This  substance  is  called 
a  dielectric.  Every  form  of  mercury  inter- 
rupter requires  a  condenser. 


28 


MERCURY  INTERRUPTER 


DIP  TYPE: 

Parts:  I.  Metal  point  or  dip. 

2.  Mercury   (stationary). 

3.  Dielectric    (alcohol,    oil   or   gas). 

4.  Motor  and  its  control. 

The  mercury  is  in  a  metal  vessel  covered 
with  alcohol.  The  motor  plunges  a  needle 
rapidly  in  and  out  of  the  mercury  pool.     The 


A  - 


Fig.  2". — Ring  type  mercury  interrupter.     (Morton.) 

frequency  and  length  of  interruptions  are  reg- 
ulated by  the  amount  of  metal  plunged  into 
the  mercury  and  the  rapidity  of  its  insertion. 
The  interrupter  must  be  in  action  before  the 
current  is  switched  into  the  primary. 


CENTRIFUGAL  TYPE: 

These  are  all  so  designed  that  the  current  is 
broken  for  a  longer  time  than  it  is  ftiade. 
There  are  two  forms  in  common  use : 

1.  JET  FORM   (Fig.  26)  : 
Parts : 

1.  Mercury  (movable  jet)   (J). 

2.  Contacts,  two  to  four  of  copper  or  phosphor- 

bronze  (P). 

3.  Dielectric   (gas,  liquid    paraffine,  or  alcohol). 

4.  Motor  and  its  control   (M). 

The  mercury  is  in  a  metal  vessel  in  which 
the  di-electric  (gas)  is  allowed  to  enter.  A 
hollow  cone-shaped  part  (C)  containing  two 
jets  at  its  base  dips  into  this  and  when  rotated 
raises  a  column  of  mercury  and  ejects  it 
through  the  openings  in  jets  against  the  sta- 
tionary metal  contacts.  The  number  of  con- 
tact teeth  inay  be  such  that  the  interruptions 
take  place  from  four  to  eight  times  per  revo- 
lution. 

2.  RING  FORM    (Figs.  27,  28)  : 
Parts  : 

1.  Alercury    (revolving  ring)    (Hg). 

2.  Contacts — revolving  eccentric  fiber  disc  (D) 
with  metal  segment  (S). 

3.  Dielectric    (liquid   paraffin). 

4.  Motor  and  its  control   (AI). 

The  mercury,  covered  with  paraffin  oil, 
is  in  a  pear-shaped  bowl,  (C)  which,  when  ro- 
tated is  raised  by  centrifugal  force  to  a  groove 
in  the  upper  part  of  the  container,  thus  mak- 
ing a  revolving  ring  of  mercury.  Inside  the 
bowl,  mounted  so  as  to  move  freely,  is  a  fiber 
disc  with  copper  or  tantalum  segments.  The 
disc  is  excentrically  disposed  to  the  rotating 
mercury  ring.  When  the  rotating  mercury  ring 
and  the  copper  segment  on  the  rotating  fiber 
disc  are  in  contact  the  primary  circuit  is  made 
and  when  the  segment  leaves  the  mercury  and 
the  fiber  part  enters  the  circuit  is  broken. 

Because  of  the  centrifugal  motion  the  mer- 
cury does  not  adhere  to  the  disc  and  the  break 
of  the  circuit  is  sudden,  sharp  and  complete. 

By  varying  the  speed  of  the  rotation  of  the 
mercury  ring  and  by  inserting  more  or  less 
of  the  fiber  Itisc  into  the  ring,  the  number  and 
length  of  interruptions  may  be  varied.  (Fig. 
28.) 


ELECTROLYTIC  INTERRUPTER 


29 


As  many  as  200  interruptions  per  second 
may  be  obtained  from  some  t_\-pes  of  mercury 
interrupters.  But  for  modern  coils  with  their 
large  iron  cores  such  very  rapid  interruptions 
do  not  result  in  the  production  of  the  maxi- 
mum output  of  current  free  from  inverse.  A 
slower  rate  of  interruption  with  complete  de- 
magnetization of  the  core  which  increases  the 
intensity  of  the  individual  discharges  is  to  be 
sought. 

One  of  the  disadvantages  of  the  mercury 
interrupter  is  the  necessity  of  cleansing  the 
mercury  when  a  di-electric  like  oil  is  used. 
The  mercury  must  be  washed  in  run- 
ning water  which  must  be  thoroughly  re- 
moved before  the  mercury  is  used  again. 
When  alcohol  is  the  di-electric,  this  cleansing 
is  not  so  frequently  necessary  and  may  be 
easily  accomplished  by  allowing  the  alcohol 
to  evaporate '  pulverizing  the  black  granular 
masses  and  discarding  the  black  powder  (mer- 
curic oxide)   remaining. 

When  illuminating  gas  is  used,  cleaning  the 
mercury  is  rarely  necessary. 

Gas   is  the  most   suitable   di-electric   where 


in^^-^ 


Fig. 


28. — Cross  section  of  ring  type  of  break.  The 
fibers  disc  bearing  the  metallic  segment  is  deep 
within  the  ring  of  mercury  at  ( i )  with  the  re- 
sultant current  curve  as  shown  below  (i).  In 
II  the  disc  is  just  in  contact  with  the  mercury 
ring  with  the  resultant  current  curve  as  shown 
in  II.     (Gocht.) 


it  can  be  used  because  not  only  does  it  re- 
quire less  condenser  but  it  is  conducive  to  a 
more  sudden  and  complete  quenching  of  the 
spark  than  is  obtained  with  alcohol  or  .oil. 


THE  ELECTROLYTIC  INTERRUPTER 
This  interrupter  was  first  described  by 
\\'ehnelt.  Its  action  is  liased  on  the  principle 
that  a  conductor  which  has  a  current  flowing 
through  it,  becomes  heated,  the  quantity  of 
heat  being  projjortional  to  the  time  and  in- 
tensitv  of  the  current  and  the  resistance  of  the 


Dilute 

Ho  so. 


\/ 


Fig.  29. — Showing   internal   arrangement  of  electro- 
lytic interrupter.   (Morton.) 

circuit.  The  interrupter  consists  of  two  elec- 
trodes, a  platinum  point  as  anode  and  a  lead 
plate  as  cathode  immersed  in  a  30-35%  solution 
of  sulphuric  acid.  The  containing  vessel  should 
have  a  capacity  of  5  gallons.  An  automatic  float 
indicator  should  be  provided  to  show  the 
height  of  the  electrolyte  which  should  be  re- 
movable from  the  containing  vessel  without 
removing  the  interrupter  elements.  The  plati- 
num wire  usually  about  1"  long  and  .07"  in 
diameter  fused  to  a  rod  of  lead  is  so  en- 
sheathed  in  a  porcelain  tube  that  any  length 
of  it  may  be  immersed  through  a  hole  in  the 
tube  into  which  it  fits  snugly.  The  tube  should 
have  a  discharge  spout  J/"  long.  If  the 
current  is  passed  into  the  interrupter,  the 
acid  surrounding  the  platintuii  point  is 
brought  to  a  boiling  point  and  electrolysis 
occurs  and  thus  a  bubble  of  gas  forms 
over  the  anode,  which  interrupts  the  cur- 
rent.   Because  of  the  self-induction  in  the  pri- 


30 


ELECTROLYTIC  INTERRUPTER 


mary  current,  a  spark  is  generated  which  leaps 
across  the  gap  and  dissipates  the  gas  about  the 
anode,  thus  permitting  the  current  to  pass 
again.  This  is  repeated  as  many  as  two  thou- 
sand times  per  second  with  small  point  ( 10 
times  as  many  interruptions  as  in  the  fastest 
mercury  break), though  with  large  point  as  few 
as  two  hundred  may  be  obtained.  Not  only 
by  varying  the  size  of  the  platinum  of  the 
anode,  but  by  changing  the  current  and  self- 
induction  of  the  primary  circuit  an  increase 
or  decrease  of  the  number  of  interruptions 
may  be  obtained.  Even  though  in  this  form 
of  interrupter  the  break  is  more  sudden  than 
the  make  there  is  nevertheless  considerable 
inverse  current. 

When  working  under  normal  conditions  the 
noise  of  the  interrupter  is  a  loud  roar  and  a 


Fig.   30. — Alultiple   point   Wehnelt   interrupter. 

violet  light  is  seen  at  the  anode  about  which 
numerous  bubbles  of  gas  are  visible.  With 
the  direct  current  the  platinum  is  normally 
consumed  but  slowly.  Should  the  polarity  be 
reversed  the  anode  disintegrates  quickly.  The 
final  heating  of  the  entire  liquid  increases  the 
resistance  and  the  consumption  of  current. 
When  the  temperature  of  90°  C.  is  attained, 
the  interrupter  works  irregularly  and  finally 
its  action  ceases. 

For  prolonged  use  a  cold  water  jacket  is 
necessary,  since  polarization  with  melting  and 
disintegration  of  the  anode  may  take  place 
from  undue  heating.  Instead  of  sending 
heavy  current  through  single  points,  inter- 
rupters with  two  to  six  points  may  be  utilized, 
each   one   being  set   for   the   same   amperage, 


and  connected  in  parallel.  It  is  important  that 
the  negative  plate  is  of  sufficient  size.  Means 
should  be  provided  for  the  escape  of  gas 
fumes. 

The  electrolytic  interrupter  has  many  prac- 
tical advantages,  because  of  its  simplicity,  the 
ease  of  its  regulation,  its  high  rate  of  inter- 
ruptions even  with  large  currents  and  its 
cheapness.  Besides  this  no  condenser  is  neces- 
sary. The  interrupter  is  really  efficient  and 
useful  only  with  a  direct  current  of  at  least 
fifty  volts.  If  the  alternating  current  only  is 
available  and  rectification  by  chemical  or  me- 
chanical means  impossible  it  may  be  used  di- 
rectly, with  a  resulting  rapid  disintegration  of 
the  anode.  An  excellent  substitute  in  these 
cases  for  platinum  is  nickel,  the  rod  of  metal 
being  so  fixed  in  the  porcelain  tube  that  it 
rests  on  a  porcelain  bottom  and  automatically 
feeds  into  the  acid,  as  it  is  consumed. 

The  electrolvtic  interrupter  has  several  dis- 
advantages. 

Generally  speaking  the  coil  works  at  less 
efficiency  with  this  interrupter  than  in  any 
other  for  the  amount  of  current  consumed. 
More  or  less  inverse  discharge  is  always  pres- 
ent. The  action  of  the  interrupter  is  noisy 
and  the  fumes  of  sulphite  of  hydrogen  gas 
generated  are  disagreeable.  The  interrupter 
cannot  be  used  for  prolonged  periods. 

The  Coil  Outfit  as  a  JVIioIe.  The  necessary 
parts  of  a  coil  outfit  are : 

1.  The  ceil. 

2.  The  interrupter. 

3.  The  rheostat. 

a)  for  primary  controh 

b)  for    control    of    mercury    and    mechanical 

interrupters. 

4.  Meters. 
Voltmeter. 
Amperemeter. 
Milliamperemeter. 

5.  Switches. 
Primary. 

a)  Hand. 

b)  Foot. 
Interrupter. 

6.  Accessories. 

a)  Fuses. 

b)  Pilot  lamp. 


COIL  EQUIPMENT 


31 


All  these  must  be  placed  in  an  electric  cir- 
cuit. 

With  an  induction  coil,  therefore,  the  prim- 
ary circuit  consists  of  a  coil  of  coarse  wire 
wound  around  a  bundle  of  soft  iron  wires  or 
rods,  the  conductors  connecting  the  coils  with 
the  dynamo  and  the  necessary  control  and 
circuit-breaking  devices  and  an  interrupter 
with  or  without  condenser. 

The  primary  current  which  is  of  low  voltage 
and  carries  heavy  amperage  is  controllable  by 
means  of  the  rheostat. 

The  secondary  circuit  consists  of  a  large 
coil  of  very  fine  wire  carrying  a  very  high  volt- 
age but  small  current  (milHamperes)  controll- 
able only  indirectly  through  the  primary  cir- 
cuit and  containing  milliamperemeter,  commu- 
tating  devices,  (spark-gap.  valve  tubes),  and 
a  capacity — a  vacuum  tube. 

With  a  properly  constructed  switch  board 
manipulation  at  the  coil  becomes  unnecessary. 
The  coil  may  therefore  be  mounted  on  the  wall 
in  front  of  or  above  the  protective  screen,  the 
switchboard  being  placed  behind  the  protec- 
tive screen.  The  direct  current  from  the 
main,  controlled  by  a  main  switch  and  prop- 
erly fused  and  carried  by  wires  of  sufficient 
diameter  to  maintain  the  voltage  without  a 
drop  even  under  considerable  load  is  brought 
to  the  control  switch  on  the  board  which 
should  be  of  the  reversing  type.  A  pilot  lamp 
indicates  whether  or  not  the  current  enters  the 
board  circuit.  If  a  single  point  electrolytic  in- 
terrupter is  utilized,  it  must  necessarily  be 
placed  near  the  switchboard,  because  of  the 
need  of  constant  regulation,  but  an  interrupter 
with  several  points  may  be  placed  at  such  a  dis- 
tance that  the  noise  is  avoided  and  the  fumes 
carried  off.  The  several  points  singly  or  in 
parallel  may  be  utilized,  as  becomes  necessary 
by  means  of  switches  on  the  switchboard. 
Usually  more  than  one  interrupter  is  connected 
to  the  switchboard,  and  by  means  of  isolated 
switches  any  type  may  be  selected  for  the 
work  at  hand,  the  mechanical  or  mercury 
for  fluoroscopy  or  treatment  and  the  multi- 
point W'ehnelt  for  radiography.  The  rheostat 
is    to    be    such    a'    construction    as    to    per- 


mit  control   of  large  currents   without  undue 
heating. 

The  rheostat  for  the  control  of  the  current 
in  the  primary  circuit  is  mounted  at  the  side 
of  the  control  board.  The  resistance  coils  are 
so  arranged  that  one  or  more  may  be  thrown 
into  the  circuit.  If  the  voltage  of  the  supply  is 
220  and  if  there  are  ten  coils  of  wire  in  the 
rheostat,  the  difference  in  e.  m.  f.  between 
two  ends  of  any  single  coil  will  be  twenty-two 
volts.  Thus,  if  three  coils  are  placed  in  the 
circuit,  by  placing  the  rheostat  handle  at  the 
third  button  to  which  the  end  of  this  coil  is 


Fig.  31. — Rheostat.  Each  coil  of  the  eight  coils  is 
composed  of  two  lengths  of  spiral  wires.  The 
difference  in  potential  between  the  ends  of  any 
single  length  is  i/i6  of  the  e.  m.  f.  of  the  supply. 
If  this  is  220,  then  the  difference  in  potential 
between  any  two  spiral  coils  will  be  13.75  volts. 
If  the  lever  is  at  button  No.  8,  only  206.25  volts 
will  go  to  the  coil.  If  on  button  No.  7,  the  fall 
in  potential  is  41.25.  and  178.75  goes  through 
the  primary. 

brought  there  will  be  but  one  hundred  and 
fifty-four  volts  entering  the  induction  coil. 
When  a  rheostat  is  not  available,  a  bank  of 
incandescent  lamps  may  be  placed  in  the  cir- 
cuit. The  lamps  of  various  candle  power  have 
a  varj'ing  resistance,  the  smaller  the  candle 
power  the  higher  the  resistance,  the  carbon 
lamp  having  a  higher  resistance  than  the 
tungsten. 

The  amperemeter  in  series  in  the  primary 


32 


SWITCH  BOARD 


circuit  and  a  milliampere  meter  in  the  second- 
ary are  necessary  instruments.  The  voltmeter 
is  connected  in  parallel. 

The  ammeter  and  milliammeter  should  be  of 
the  "  dead  beat "  variety,  and  should  have 
ranges  from  0-100  amperes  and  0-150  milli- 
amperes  respectively.     They  must  be  mounted 


Fig.  32. — Diagram  of  connection  of  a  coil  outfit. 
The  platinum  point  of  the  Wehnelt  interrupter 
is  positive.  The  voltmeter  is  connected  in  paral- 
lel.    The  ammeter  in  series. 

SO  that  their  faces  are  inclined  at  an  angle  of 
approximately  45  degrees  from  the  horizontal; 
that  they  may  be  easily  read. 

The  preliminary  regulation  of  the  electro- 
lytic interrupter  points  must  be  made  by 
means  of  the  amperemeter,  each  point  being 
sufficiently  immersed  in  the  solution  to  indi- 
cate a  certain  number  of  amperes.  The  foot 
switch  is  of  value  for  fluoroscopy  when  the 
switchboard  is  at  a  distance  from  the  fluoro- 
scopic stative. 


The  primary  switch  must  be  of  the  single 
pole,  quick  break  variety  and  must  be  so  con- 
structed that  the  actual  breaking  takes  ^lace 
below  the  surface  of  the  switchboard.  All 
current-carrying  portions  must  be  heavy 
enough  to  carry  and  break  the  maximum  pri- 
mary current. 

The  pole  changer  should  consist  of  a  two- 
pole,  double-throw  switch  with  the  current- 
carrying  portions  of  sufficient  cross-section  to 
carry  the  maximum  primary  current  without 
undue  heating. 

The  inductance  switch  must  consist  of  a 
lever   switch,   capable   of   carrying  the  maxi- 


mum  primary 


current   and   so   designed  that 


the  inductance  on  which  the  machine  is 
operating"  can  be  read  directly  from  the  switch 
itself.  There  should  be  dead  buttons  separat- 
ing the  inductances. 

The  assembling  of  the  coil  outfit  is,  of 
course,  simplified  when  a  switchboard  is  pro- 
vided, wired  by  the  manufacturer. 

Szvitchboard :  The  switchboard  must  have 
the  following  control  and  measuring  instru- 
ments mounted  on  it,  and  be  removable  and 
demoimtable  at  a  distance  from  the  coil.  It 
should  be  of  marble,  and  mounted  on  a  stand 
having  ball  bearing  casters. 

1.  A  primary  switch. 

2.  A  pole  changer. 

3.  An  ammeter  with  scale  reading  from  0 
to  100. 

4.  Switches  for  connecting  the  points  of  the 
electrolytic  interrupter. 

5.  Switch  for  starting  the  motor  of  the  mer- 
cury interrupter. 

6.  Switch  for  connecting  mercury  inter- 
rupter. 

7.  Speed  regulator  for  controlling  the  speed 
of  the  above  motor,  having  a  range  of  not 
less  than  50  r.  p.  m.  to  full  speed. 

8.  Switch  for  connecting  the  points  of  the 
condensers,   collectively. 

9.  Switch  for  connecting  separately  any  one 
of  the  points,  of  the  primarj'  winding. 

10.  Line  switch,  including  automatic  circuit 
breaker,  of  a  suitable  capacity. 

11.  Pilot  lights,  suitably  shaded. 


COXXECTIONS   OF  COIL  OUTFIT 


33 


12.  Connections  for  attaching  foot  switch, 
controlhng  room  lights  and  tube  current  sup- 
ply. 

13.  Cords  arranged  so  that  variable  spark 
gap  can  be  regulated  from  the  board. 

14.  A  rheostat  connected  with  the  supply, 
and  capable  of  operating  for  not  less  than  one 
hour,  with  all  the  resistance  in,  without  undue 
heating. 

When  the  switchboard  is  not  available  the 
above  mentioned  parts  must  be  assembled  into 
a  working  unit. 

Diagram  (  Fig.  32)  gives  a  simple  scheme  for 
the  connecting  of  the  various  essential  parts 
of  a  coil  outfit.  When  amplified  by  the  inser- 
tion of  switches  for  reversing  the  primary  cur- 
rent, multiple  interrupters  and  condenser,  pilot 
lamps,  etc.,  these  are  connected  in  series  or 
parallel  in  the  same  way,  the  essential  parts 
and  arrangements  of  the  circuit  as  shown  in 
the   simple   installation   being   maintained. 

Wherever  the  direct  current  is  avail- 
able, 110  or  220  volts  may  be  used  with  any 
form  of  interrupter  and  a  coil,  without  any 
changes.  Where  a  heavy  amperage  is  to  be 
employed,  it  is  better  to  use  a  voltage  of  220. 

Where  only  alternating  current  is  available 
it  may  be  used  directly  with  a  special  form  of 
mechanical    or    an    electrolytic    break,    which 


utilizes  nickel  for  the  anode  instead  of  plati- 
num. It  is  better  however  to  commutate  this 
current  by  the  means  already  discussed  or 
utilize  a  step-up  closed  core  transformer,  the 
so-called  interrupterless  machine  as  the  ener- 
gizing apparatus. 

If  an  electrolytic  rectifier  be  employed  in 
connection  with  a  \\'ehnelt  interrupter  on 
A.  C,  it  is  wise  to  employ  220  volts  A.  C, 
in  order  to  prevent  excessive  voltage  drop. 

A  tube  energized  by  a  coil  discharge  is 
regulated  by  the  same  method  as  a  tube  which 
is  energized  by  a  closed-core  transformer. 
The  energizing  current  is  controlled  by  regu- 
lating the  primary  amperage  by  the  inter- 
rupter and  rheostat.  If  a  single  point  is  used, 
this  is  plunged  into  the  acid  until  the  required 
gap  is  obtained  With  a  multiple  point  inter- 
rupter, each  point  is  set  to  take  a  certain  equal 
amount  of  current  and' then  all  the  points  are 
connected  in  multiple  distribution  and  the  re- 
sulting current  is  controlled  by  the  rheostat. 
\\'ith  a  gas  tube  the  vaciuuu  is  reduced  until 
the  sparking  across  the  gap  desired  ceases. 

If  only  5  to  7  milliamperes  be  used,  a  set 
distance  between  regulator  and  cathode  ter- 
minal will  automatically  regulate  the  tube  to 
twice  the  distance  in  inches  spark  back-up 
across  the  terminals. 


CHAPTER  III 

INDUCTION    APPARATUS— CLOSED 

CORE— INTERRUPTERLESS 

The  ideal  and  most  efficient  apparatus,  where 
alternating  current  is  available,  by  which  to 
obtain  a  high  tension  alternating  current  is  a 
closed  core   transformer.     The   core   consists 


Fig.    33. — Closed    magnetic    circuit    transformer. 

of  laminated  iron  or  prepared  silicon  steel  in 
circular  or  rectangular  form, — a  closed  ring  or 
ti  parallelogram.  The  primary  winding  is 
placed  on  one  arm  or  side  and  the  secondary 
winding  is  placed  on  the  opposite.  But  they 
may  both  be  placed  on  the  same  arm,  over  or 
adjoining    each    other.       Practically    all    the 


magnetic  lines  of  force  are  thus  utilized.  There 
is  a  minimal  amount  of  magnetic  leakage  or 
stray  magnetism  which  is  not  enclosed  by  the 
secondary  but  for  practical  purposes  it  may  be 
neglected  and  assumed  that  the  induced  e.  m.  f . 
per  turn  of  wire  in  the  secondary  is  the  same 
as  in  the  primary. 

Since  the  secondary  and  primary  coils  are 
both  wound  on  the  same  core,  it  follows  that 
the  actual  voltage  induced  will  be  directly 
proportional  to  the  number  of  turns  of  wire 
in  both  coils.  The  ratio  of  primary  to  second- 
ary voltage  will  thus  depend  upon  the  ratio  of 
primary  to  secondary  windings. 

Thus,  if  the  primary  winding  consists  of  50 
turns  of  wire,  all  in  series,  while  the  secondary 
has  1,000  turns,  the  ratio  of  turns  is  1 :20  and 
this  will  also  be  the  ratio  of  primary  impressed 
e.  m.  f.  to  secondary  induced  e.  m.  f.  on  the  as- 
sumption that  there  is  no  magnetic  leakage 
and  a  negligible  internal  resistance  in  the 
primary.  One  hundred  and  ten  volts  would  un- 
der these  conditions  be  stepped  up  to  2200 
volts.  The  total  wattage  of  the  secondary 
current  is,  aside  from  a  small  loss,  due  to 
internal  resistance,  the  same  as  the  wattage  of 
the  primary.  If  110  volts  and  2  amperes  flow 
through  the  primary,  the  secondary  watt- 
age will  also  be  220,  therefore  the  amperage 
of  the  secondary  discharge  would  be  1/10  of 
an  ampere  or  100  milliamperes. 

The  primary  is  usually  wound  in  several 
layers  or  sections.  These  are  arranged  to  give 
different  voltages  and  when  the  full  line  volt- 
age is  used  without  rheostat  control,  the  sec- 
ondary output- is  fairly  constant,  for  the  par- 
ticular winding  used  with  the  same  resistance 
in  the  secondary  circuit. 

Because  of  the  oscillation  of  the  current 
from  zero  to  maximum  the  alternating  current 
is  analogous  in  action  on  the  transformer 
to  the  action  of  the  direct  current  and  inter- 
rupter in  the  induction  coil.  The  current, 
however,  reverses  its  direction  not  with  the 
make  and  break,  but  the  change  in  direction 
of  the  primary  flow. 


CLOSED  CORE  TRANSFORMER 


35 


The  high  potential  current  in  the  secondary 
is  alternating,  differing  from  that  produced  by 
an  induction  coil  in  being  more  nearly  equal  in 
both  phases.  For  utilization  in  an  x-ray  tube 
it  must  of  course  be  made  unidirectional.   This 


Core- 


■Jccori(/ary 


)       4  q/npef£3 

^S  7e//r73 


Fig.  33a. — Illustrating  the  principles  of  transformer 
action. 


is  done  by  a  rectifying  switch  or  rotary  pole 
changer.  This  changes  the  direction  of  the 
inverse  wave,  so  that  the  high  tension  alter- 
nating current  is  practically  transformed  into 

e  f 

S  i    -    d 

c 


Fig.  34. — Diagram  of  construction  of  a  closed  core 
transformer.  The  primary  and  secondary  are 
wound  on  the  same  arm.  ab — iron  core,  gh — 
primary  winding,  cd — insulating  material,  ef — 
secondary  terminals. 

a  high  tension  direct  pulsating  current,  both 
inductive  phases  of  the  alternating  current  be- 
ing utilized. 

The  efficiency  of  such  a  transformer  is  far 
higher  than  that  of  a  coil.  The  term  "  effi- 
ciency "  denotes  the  value  of  the  ratio  of  out- 
put to  the  input.  The  diff"erence  is  the  power 
lost.  These  losses  are  due  to  the  internal 
resistance  of  the  copper  wire  and  to  the  loss 


of  power  from  hysteresis  and  eddy  currents. 
The  efficiency  of  the  transformation  in  a  coil 
is  only  about  fifty  to  seventy-five  per  cent, 
because  of  magnetic  leakage.  The  efficiency 
of  the  alternating  current  transformer  is 
about  95%,  but  its  actual  value  will  depend 
to  a  certain  extent  upon  the  design,  amount 
and  quality  of  the  materials  used.  There 
should  be  sufficient  cross  section  of  laminated 
iron  of  proper  quality  and  these  laminations 
must  be  well  insulated.  The  primary  winding 
must  be  ample  so  as  to  "  choke  "  efficiently. 
Its  core  is  of  course  not  as  rapidly  demagnet- 
ized as  the  straight  iron  core,  and  how  this 
influences  the  form  of  the  secondary  dis- 
charge will  be  shown  later. 

The  transformer  may  be  oil  immersed  or 
dry.  For  the  higher  voltage  the  former  is  to 
be  preferred.  For  x-ray  work  it  may  be  wound 
for  voltages  as  high  as  120,000  to  135,000 
volts.  The  efficiency  of  a  small  transformer 
will  necessarily  be  lower  than  that  of  a  larger 
transformer.  The  maximum  efficiency  should 
generally  be  reached  at  from  three-quarters 
to  full  load.  When  the  secondary  of  a  trans- 
former is  on  open  circuit  there  is  "  no  load  " 
upon  it.  This  circuit  may  be  closed  through 
the  "  load  "  of  an  x-ray  tube  or  other  "  non- 
inductive  "  resistance. 

The  capacity  of  a  transformer  may  be  as- 
certained by  noting  the  number  of  milli- 
amperes  obtainable  at  a  certain  gap,  through 
a  standard  tube.  The  efficiency  of  a  trans- 
former may  be  best  estimated  by  determining 
the  drop  in  voltage,  following  a  fixed  increase 
in  milliamperage.  Thus  if  one  transformer 
drops  10,000  volts  for  every  increase  in  load 
of  15  milliamperes  and  another  drops  the 
same  voltage  for  an  increase  of  only  10  milli- 
amperes, then  the  former  is  the  more  efficient 
as  a  transformer  of  electrical  energy.  This 
may  be  graphically  determined  by  plotting  the 
voltage  current  curve. 

It  must  be  borne  in  mind  that  the  tempera- 
ture rise  is  no  indication  of  the  amount  of 
power  lost  in  the  transformer;  a  transformer 
which  gets  very  hot  may  be  more  efficient  than 
another    which    remains    comparativelv    cool. 


36 


IXTERRUPTERLESS  MACHIXE 


Temperature  rise  must  only  be  considered 
with  reference  to  the  effect  it  may  have  upon 
the  materials  used  in  the  construction  of  the 
transformer. 

The  middle  of  the  secondary  winding  is 
usually  grounded.  This  is  a  safety  measure 
to  prevent  the  full  voltage  from  discharging 
to  persons  accidentally  coming  in  contact  with 
the  secondary  circuit. 

To  prevent  surges  which  may  damage  the 
transformer  a  resistance  is  placed  across  the 
low  tension  terminals  of  the  primary.  An 
ordinary  incandescent  bulb  may  be  used. 

The  Interrupterless  High  Tension 
Appar.atus. 

The  machines  are  known  by  the  kilowattage 
they  are  capable  of  delivering.  Thus  a  6 
K.  V.  A.  220  volt  transformer  is  one  deliver- 
ing 6000  watts  at  full  load  and  operated  at 
220  volts. 

The  machines  in  use  consist  of  the  follow- 
ing parts : 

1.  Rotarv — (either  inverted  rotary  con- 
verter or  synchronous  motor  ) . 

2.  Transformer — oil  immersed  or  dry. 

3.  Commutator — mounted  on  shaft  of  ro- 
tary. 

4.  Accessories. 

The  purpose  and  variety  of  rotary  depends 
on  the  current  supply  whether  A.  C,  or  D.  C. 

Where  the  direct  current  only  is  available 
this  type  of  apparatus  may  be  utilized  by 
employing  an-  alternator  which  is  a  rotary 
converter  to  change  the  direct  current 
into  alternating.  This  low  tension  single 
phase  alternating  current  drawn  from  two 
slip  rings  of  the  rotary  is  now  passed  into  the 
primary  of  the  transformer,  through  a  switch 
on  the  control  board  which  permits  the  use 
of  varying  inductances,  (varying  lengths  of 
primary  windings ) ,  or  the  use  of  an  auto- 
transformer,  for  the  purpose  of  maintaining 
the  voltage. 

Transformer:  The  transformer  should  be 
placed  in  a  metal  container,  well  filled  with  oil, 
which  should  be  moisture  free.  The  oil  should 
te  replenished  from  time  to  time,  to  keep  the 


transformer  completely  immersed.  The  trans- 
former should  be  of  the  closed-core  type  with 
small  magnetic  leakage.  The  transformer 
should  have  a  rating  of  not  less  than  12  kilo- 
volt  amperes   for  radiographic  purposes. 

Under  operating  conditions  it  should  deliver 
a  normal  rectified  spark  not  less  than  10  inches 
in  length.  The  transformer  should  have 
an  electrical  efficiency  of  not  less  than  90%, 
and  should  maintain  full  voltage  at  full  load 
within  8%,  provided  the  drop  across  the  line 
is  not  greater  than  3%.  X'oltages  from  30,- 
000,  to  120,000  should  be  attainable  by  the  use 
of  the  auto-transformer  device,  in  steps  of 
5,000  volts. 

Motors:  The  alternating-current  inter- 
rupterless x-ray  apparatus  should  be  equipped 
with  a  self-starting  synchronous  motor,  which 
should  automatically  go  into  synchronism 
when  starting  switch  is  closed.  This  motor 
should  start  directly  off  the  220  volt  line  by 
the  use  of  a  single-throw  switch,  and  operate 
the  high-tension  rectifying  switch  without  any 
slip  whatever  from  absolute  synchronism  and 
without  overheating  under  normal  operating 
conditions.  Since  the  rectifier  of  a  60  cycle 
current  must  make  a  J4  turn  each  1/20  of  a- 
second,  the  motor  must  make  1,800  revolu- 
tions per  minute.  The  direct  current  motors 
acting  as  rotary  converters  should  be  of  ample 
capacity  and  fitted  with  automatic  starting 
devices. 

The  motors  of  the  interrupterless  machine 
must  receive  constant  care  and  attention,  if 
the  machine  is  to  work  at  its  full  efficiency. 
The  bearings  should  be  properly  oiled  with 
heavy  machine  oil  and  the  slip  rings  and  com- 
mutators kept  clean  and  free  from  carbon  de- 
posit, by  the  use  of  00  sand-paper  and  rub- 
bing with  vaseline.  This  is  more  necessary  in 
a  direct  current  machine  with  a  rotary  con- 
verter because  the  energy  passes  into  the 
motor  through  the  D.  C.  brushes  and  out 
through  the  slip  rings,  while  in  the  A.  C. 
machine  the  transformer  current,  does  not 
pass  through  the  motor.  The  contact  between 
the  brushes  and  the  commutators  must  be  firm 
and    even.      Protection    from    sparks    due    to 


DISC  COMMUTATION 


Z7 


surges  should  be  afforded.  In  making  the 
connections  the  line  should  be  properly  fused. 

The  high  tension  rectifying  or  rotaiy  pole 
changers  are  mounted  upon  the  shaft  of  the 
motor  converter  or  when  the  alternating  cur- 
rent is  used  on  the  shaft  of  the  self-starting 
synchronous  motor.  These  high  tension 
rectifying  devices  must  be  correctly  adjusted 
in  relation  to  the  motor  armature  or  to  the 
cycles  of  A.  C.  current. 

There  are  generally  speaking  two  types  of 
rectifying  devices  the  "  disc  "  and  the  ''  arm." 
They  are  similar  in  their  action. 

Disc  Coiiuiiiitation :  This  consists  of  a 
round  micanite  disc.  To  the  periphery  of  this 
disc  are  fastened  copper  strips,  opposite  each 
other,  and  occupying  a  little  more  than  a 
quarter  of  the  circumference.  The  collector 
brushes  are  mounted  on  bakelite  support 
pieces  to  prevent  creepage.  They  are  arranged 
to  commutate  the  current  and  rectify  the  high- 
tension  alternating  current.  The  alternating 
current  enters,  so  to  speak,  at  two  opposite 
contacts,  and  the  rectified  current  is  taken 
from  the  two  remaining  contacts  and  con- 
ducted by  the  outlet  terminals. 

Figure  35  gives  a  diagrammatic  idea  of  the 
rectifying  device.    "  F  "  is  the  mica  disc,  "  G  " 


^    B 


Fig.  35. — Diagrammatic  scheme  of  rectifying  device. 

and  "  H  "  are  two  copper  commutator  strips 
fastened  to  the  periphery  of  the  disc,  and 
placed  opposite  each  other.  "  J  "  and  "  K  " 
are   high-tension   alternating   current   brushes 


which  receive  the  discharge  from  the  trans- 
former through  leads  1  and  2.  "  L "  and 
"  M  "  are  the  brushes  which  receive  the  recti- 
fied current  and  3  and  4  are  conduits  which 
lead  it  to  the  tube.  For  one  complete  cycle, 
or  two  alternations,  the  disc  makes  half  a 
revolution. 


^-K^^ 


Fig.  36. — Diagrammatic  scheme  showing  reversal  of 
wave. 


The  wave  form  "  c "  shows  the  first 
alternation  during  this  period;  the  disc  has 
made  a  quarter  of  a  revolution  and  attained 
the  position  shown. 

If  lead  No.  1  is  of  negative  polarity 
at  that  instant,  the  direction  of  the  flow  is  then 
indicated  by  the  arrows.  In  Fig.  36,  the  next 
alternation  and  its  reversal  is  shown.  The  disc 
has  now  changed  its  position.  Conduit  No.  2 
is  now  negative  and  the  current  flows  from 
the  transformer  as  shown  by  the  arrows.  The 
polarity  of  the  discharge  has  still  been  main- 
tained as  may  be  seen  by  studying  the  arrows 
in  Fig.  36,  showing  that  all  the  positive  im- 
pulses are  conducted  along  No.  3.  and  the 
negative  impulses  along  No.  4,  thus  giving 
absolute  unidirectional  current.  Wave  D 
(Fig.  36)  has  now  been  reversed  as  shown 
between  3  and  4. 

But  the  entire  wave  is  not  utilized,  for  the 
base  of  the  wave  being  a  current  of  relatively 
low  voltage  would  generate  rays  of  undesir- 
ably low  penetration  and  needlessly  heat  the 


38 


WIRING  DIAGRAM  D.  C.  MACHINE 


LINE  iVnXH 


^ 


mLUAMTERE   METER 


\SL^ 


u 


VOLTAGE  SWITCH 

Pig,  37,_-Wiring  and   connections  of  rotating  4  arm  type  of  commutation  direct  current  interrupterless 
machine,  rheostat  and  multiple  inductance  control.     Snook. 


\\-IRING  DIAGRAM  A.  C.  MACHINE 


39 


V01.TACE  iWITCH 


Ftg.  38. —Scheme  of  alternating  current  interrupterless  machine.     (.Snook.) 


40 


ROTATING  ARM   COMMUTATION 


tube.  The  contacts  on  the  commutating  de- 
vices are  so  arranged  as  to  make  contact  only 
at  the  peak  of  the  wave,  where  the  highest 
voltages  are  available,  thus  obtaining  the 
maximum  current  with  the  smallest  portion 
of  the  wave. 

The  tube  therefore  energized  by  such  a  cur- 
rent does  not,  strictly  speaking,  receive  a  con- 
tinuous current  flow  but  a  large  number  of 
current  impulses  per  second.  For  practical 
purposes  the  illumination  of  the  x-ray  tube  by 
this  pulsating  current  may  be  considered  con- 
tinuous. 

Rotating  Ann  Commutation.  Figs.  37-38. 
This  consists  of  a  shaft  of  insulating  ma- 
terial in  which   are  inserted   four  arms,   one 


Fig.  39. — Wiring  diagram  of  interrupterless  trans- 
former, disc-tj'pe  commutation  rheostat  (Rh) 
and  autotransformer  (A)  control  (Pr)  is  pri- 
mary of  transformer.  (C)  is  the  primary  of 
the  Coolidge  step  down  transformer.  (T)  is 
the  time  switch.  'Mot)  is  the  motor  (Prot) 
p^otecti^e  resistance. 

pair  set  at  right  angles  to  the  other.  In 
the  circle  of  their  path  are  set  eight  metal- 
lic arcs,  four  above  and  four  below.  These 
arcs  are  arranged  in  pairs,  one  pair  being 
connected  to  each  side  of  the  secondary. 
Above,  the  two  outer  arcs  are  connected  to 
the  positive  side  and  the  two  inner  to  the 
negative  side  of  the  tube.  If  the  diagram 
(Figs.  i7 ,  38)  is  studied,  it  will  be  noted  that 
at  the  moment  the  arms  of  the  commutating 
devices  are  in  the  position  indicated,  the  high 
tension  current  is  flowing  from  the  trans- 
former, through  the  first  arc,  through  the  tirst 
arm  to  the  first  upper  sector,  through  the 
milliampere  meter  to  the  positive  side  of  the 


Fig.  40 — Wiring  diagram  and  switchboard  of  alter- 
nating current  transformer. 

tube.  The  return  is  through  the  upper  third 
sector  or  arc  and  through  the  arm  to  the  other 
side  of  the  secondary  of  the  transformer.  As 
the  polarity  of  the  transformer  discharge 
changes,  a  turn  of  the  shaft  to  ninety  degrees 


Fig.  41. — Alternating  current  interrupterless  trans- 
former with  rotating  arm  commutation.  The 
transformer  is  placed  at  the  bottom  of  the  cab- 
inet in  a  cylindrical  tank.  A  convenient  type 
permitting   accessibility. 


ACCESSORIES  INTERRUPTERLESS  MACHINE 


41 


*  Resistances  for  15  Ohms  Rheostat. 
(For  220  Volt  D.  C.  Machine  =155  A.  C.) 


Resistances   for  20   Ohms   Rheostat 
(For  220  Volt  A.  C.  Machine) 


iUtton 

Circuit 

Per    button 

I 

15.00 

2.64 

2 

12.36 

2.51 

3 

9.85 

2.00 

4 

7.85 

1.85 

5 

6.00 

1-35 

6 

4.65 

1.20 

7 

3-45 

0-95 

8 

2.50 

0.70 

9 

1.80 

0.50 

10 

1.30 

0.42 

II 

0.88 

0.32 

12 

0.56 

0.17 

13 

0.39 

O.II 

14 

0.28 

O.IO 

15 

0.18 

0.07 

i6 

O.II 

0.04 

17 

0,07 

0.03 

i8 

0.04 

0.02 

19 

0.02 

0.02 

20 

0.00 

0.00 

utton 

Circuit 

Per  button 

I 

20.00 

3-25 

2 

16.7s 

300 

3 

137s 

2-55 

4 

11.20 

2.30 

5 

8.90 

2.10 

6 

6.80 

1.60 

7 

5-20 

1-35 

8 

3.85 

I. CO 

9 

2.85 

0.7s 

10 

2.10 

0.60 

II 

i-So- 

0.40 

12 

1. 10 

0.30 

13 

0.80 

0.25 

14 

O-SS 

0.20 

IS 

0.3s 

O.IO 

16 

0.25 

0.08 

17 

0.17 

0.07 

18 

O.IO 

0.06 

19 

0.04 

0.04 

20 

0.00 

0.00 

20.00  ohms. 

Table  III 

15.00  ohms. 

T.-\BLE   II 

*  Note. — The  155  volts  a.  c.  may  be  stepped  up  to  220  volts  a.  c.  before  it  reaches  the  primarj-  by  mearts 
of  a  special  transformer    (booster  transformed)    or  autotransformer. 


makes  the  connections  of  the  transformer  to 
the  tube  through  the  second  and  fourth  arms 
such,  that  the  current  still  passes  into  the  tube 
in  the  proper  direction. 

The  high  tension  rectifying  commutators 
should  be  connected  to  the  rotary  converter  or 
to  the  synchronous  motor  directly  by  means 
of  a  flexible  coupling,  which  while  permitting 
longitudinal  flexibility  will  prevent  axial  twist. 
The  rectifying  switch  should  be  highly  in- 
sulated to  prevent  losses  from  leakage.  The 
bearings  at  the  back  ends  of  the  commutating 
switch  should  be  provided  with  sufficient 
lubrication. 

Cabixet 

The  cabinet  is  usually  of  highly-polished 
wood.  No  revolving  parts  should  be  mounted 
in  direct  mechanical  contact  with  the  cabinet. 
The  motor  should  be  enclosed  and  the  cabinet 
so  arranged  that  the  machine  may  be  taken 
down  and  set  up  conveniently.  The  supports 
of  the  machine  should  rest  on  elastic  cushions, 
so  that  the  operation  of  the  motor  and  com- 
mutator is  noiseless  and  without  vibration. 


Accessories 

Certain  accessories  are  usually  mounted  on 
the  control  stand,  which  should  be  a  separate 
unit.  It  should  contain  the  switch,  rheostat, 
cable-board,  and  fuses  placed  at  the  top  of 
the  stand  at  an  angle  convenient  to  the  oper- 
ator. The  starting  switch  should  be  a  double- 
blade  knife  switch.  The  operating  switch 
should  be  of  the  same  type,  the  contacts  being 
placed  below  the  surface  of  the  marble 
board,  and  being  equipped  with  an  auto- 
matic circuit  breaker.  The  rheostat  should 
consist  of  resistance  units  of  an  approved  tj'pe 
of  non-oxidizing  wire.  On  the  marble  board 
shall  be  mounted  a  switch  controlling  the 
variable  ratios  of  transformation  in  the  high 
tension  transformer. 

The  alternating  current  machine  should  be 
furnished  with  a  polarit\-  indicator,  to  indicate 
the  direction  of  the  flow  of  the  current. 

The  low  tension  voltmeter  may  be  con- 
nected in  a  manner  shown  in  Fig.  2>7  and  38 
so  as  to  indicate  kilovolts  between  the  sec- 
ondary terminals  of  the  transformer,  or  it  may 
be  graduated  in  inches  of  spark.  All  the  live 
parts  of  control  should  be  protected  from  con- 


42 


TRANSFORMER  CONTROL 


tact  by  being  placed  underneath  an  insulating 
surface  such  as  marble  or  glass.  Only  the 
operating  levers  should  extend  through  the 
surface  so  that  they  may  be  reached  by  the  hand 
of  the  operator.  In  the  secondary  circuit  there 
is  placed  a  double  scale  niilliamperemeter. 
the  change  in  scales  being  afifected  by  means 
of  a  shunt  so  that  the  meter  may  read  from 
1  to  20  or  1  to  200  milliamperes.  An  arrange- 
ment for  measuring  the  spark  gap  between 
the  movable  terminals  connected  to  the 
secondary  is  usually  placed  over  the  wooden 
cabinet,  which  encloses  the  transformer,  com- 
mutating  switch,  and  motor. 

COXTROL 

The  changes  in  the  voltage  produced  by  the 
transformer,  as  has  already  been  indicated, 
are  in  the  direct  ratio  of  the  number  of  turns 
in  the  primary  to  the  number  of  turns  in  the 
secondary,  and  the  changes  in  current  are  in 
inverse  ratio.  The  average  commercial  trans- 
former for  x-ray  production  has  a  ratio  of 
primary  to  secondary  winding  of  one  to  five 
hundred.  Thus  the  voltage  applied  to  the 
primary  would  be  stepped  up  five  hundred 
times  in  the  secondary' and  the  current  would 
be  but  1/500  of  that  in  the  primary. 

Thus,  if  one  hundred  volts  were  applied  to 
the  primary,  the  voltage  of  the  secondary 
would  be  50.000,  if  120  volts  60,000,  if  150 
volts  75,000.  etc.  The  secondary  voltage  is, 
therefore,  regulated  by  controlling  the  pri- 
mary voltage. 

This  may  be  done  bj-  the  following  means : 

1.  Rheostat. 

2.  Variable  inductance  with  or  without 
rheostat. 

3.  Auto-transformer. 

4.  Booster.       j 

1.  Rheostat  control.  If  the  line  supply  is 
220  volts  and  it  is  desired  to  introduce  only 
120,  sufficient  resistance  must  be  thrown  into 
the  circuit  to  consume  100  volts. 

Thus,  if  a  secondary'  output  of  fifty  milli- 
amperes at  45,000  volts  is  required,  the  pri- 
mary should  ( if  the  ratio  of  transformation  is 


1  to  500)  be  supplied  with  90  volts  and  a  cur- 
rent of  .050  X  500  =  25  amperes.  If  the  in- 
itial supply  is  220  volts,  then  enough  resistance 
must  be  introduced  in  the  circuit  to  consume 
130  volts  with  a  current  of  25  amperes. 

Since  V  =  IR,  it  follows  that  130  =,25  x  R. 
Therefore,  R  =  5  1/5  ohms.  That  is  to  say 
5  1/5  ohms  resistance  must  be  inserted  in  the 
primary  circuit.  A  glance  st  the  rheostat  re- 
sistance table  (Table  3,  page  39)  shows  that 
this  resistance  would  be  obtained  with  this 
particular  rheostat  on  the  seventeenth  button 
(the  total  resistance  of  7  to  20  =  5.20  ohms). 

The  ohmic  resistance  in  the  primary  cir- 
cuit multiplied  by  the  amperage  gives  the  loss 
in  volts  before  reaching  the  primary.  There- 
fore on  the  sixteenth  button  of  the  rheostat,  if 
the  resistance  is  1/10  ohm  (Table  II,  pg.  41) 
and  the  amperage  40,  the  loss  is  40  x  1/10  = 
4  volts.  If  the  supply  is  155  volts  A.C.  only 
151  volts  would  then  reach  the  primary.  The 
power  then  utilized  would  be  151  x  40  or 
6,040  watts  or  about  6  K.  V.  A.  If  the  ratio 
of  transformation  is  1  to  500,  the  secondary 
output  would  be  about  75,000  volts,  and  the 
6,040  watts  would  be  made  up  by  2/25  of  an 
ampere  or  80  milliamperes.  Thus  on  the  six- 
teenth button  of  the  rheostat  151  volts  and  40 
amperes  would  with  the  particular  trans- 
former be  transformed  to  75  1/2  K.  Y.  and 
80  milliamperes. 

The  current  taken  by  the  primary  really  de- 
pends on  the  current  drawn  through  the 
secondary  or  tube  circuit,  which  is  the  partic- 
ular load,  and  the  current  drawn  in  the  tube 
circuit  depends  on  the  vacuum  of  the  gas  tube 
and  the  filament  heat  in  the  Coolidge  tube. 
With  the  same  rheostat  reading,  as  more 
current  is  drawn  into  the  gas  tube,  the  pri- 
mary current  increases  and  the  secondary  vol- 
tage" falls  unless  the  rheostat  setting  is 
changed. 

This  is  the  disadvantage  of  a  rheostat  con- 
trol, in  that  the  slightest  variation  in  tube  cur- 
rent, such  as,  for  instance  may  occur  when  a 
gas  tube  becomes  heated  and  its  vacuum  falls, 
results  in  a  considerable  fall  in  voltage  with 
loss  of  penetration,  in  spite  of  the  fact  that 


AUTO-TRAXSFORMER  COXTROL 


43 


the  rheostat  setting  is  unchanged.  If,  for  ex- 
ample, the  rheostat  setting  places  a  resistance 
of  ten  ohms  in  the  primary  circuit  of  a  trans- 
former, whose  step-up  ratio  is  1  to  500,  and 
the  voltages  consumed  in  the  rheostat  under 
varying  loads  are  estimated,  the  marked  varia- 


Jl/^'e^rn-^y   i'ur^nr  ■^"^Py    'Y'"' 


=  66  l/o.'rj 


Fig.     42a. — Diagram     illustrating     auto-transformer, 
construction   and   ratios.      (Croft.) 

tion  for  the  same  resistance  becomes  apparent. 
Thus,  with  a  secondary  current  of  ten  mills., 
the  primary  current  would  be  five  amperes. 
The  voltage  consumed  would,  according  to 
Ohms  Law  (V=I  x  R)  be  5  x  10  or  50,  and 
if  the  line  supply  was  200,  then  170  volts 
would  be  impressed  across  the  primary,  giving 
a  secondary  voltage  of  85,000.  If  the  second- 
ary current  is  20  mills.,  the  voltage  consumed 
would  be  100.  This  would  leave  but  120  volts 
to  be  applied  to  the  primary  and  would  give 
a  secondary  voltage  of  but  60,000,  a  loss  of 
25,000  volts,  the  equivalent  of  nearly  1  1/2 
inches  of  spark  gap. 

2.  Variable  Iiuliictaiicc.  The  primary  wind- 
ing is  wound  and  tapped  in  such  a  way  that 
the  various  portions  of  the   winding  may  be 


used  in  series  or  in  parallel.  This  varying  the 
ratio  of  primary  to  secondary  winding  changes 
the  secondary  voltage.  The  windings,  when 
connected  in  parallel,  would  be  suitable  for 
obtaining  high  secondary  outputs  with  low  pri- 
mary voltages  and  heavy  currents. 

3.  Auto-trausformer.  To  obviate  the  fluc- 
tuation in  the  tube  load  resulting  from  pur- 
poseful and  incidental  changes  of  this  kind, 
the  so-called  auto-transformers  are  used, 
which  permit  the  maintenance  of  a  predeter- 
mined voltage  and  also  an  increase  of  current 
to  the  tube  with  very  small  voltage  drop. 
Thus,  if  the  vacuum  is  stabilized,  the  trans- 
former can  be  made  to  energize  the  tube  by 
a  definite  unvariable  voltage,  and  this  voltage 
will  stay  nearly  constant,  regardless  of  the 
load. 

This  auto-transformer  consists  of  a  pri- 
mary and  a  secondary,  but  both  are  part  of 
the  same  circuit,  in  other  words,  a  continuous 
coil  of  wire  on  an  iron  core,  which  is  tapped 
at  certain  intervals  (Figs.  42,  42a  ).  By  means 
of  a  control  handle,  the  ratio  between  the  num- 
ber of  windings  in  the  primary,  which  is  the 
entire  length  of  the  coil  and  the  secondary, 
which  is  the  variable  length  of  the  same,  is 
changed. 


Main  Line 


F:c.    42, — .'Xuto    transformer   construction    and    con- 
nections.    U.  S.  .■\rmy  Manual. 

Thus  higher  or  lower  voltages  are  applied 
to  the  primary  of  the  transformer.  The  auto- 
transformer  is  really  a  low  ratio,  step-down, 
alternating  current  transformer  made  of  a 
single  coil  of  heavy  copper  wire,  acting  on  the 
principle  of  auto  or  self-induction.  The  sec- 
ondary e.  m.  f.  induced  in  the  variable  length 


44 


BOOSTER  TRANSFORMER 


of  winding  is  due  in  part  to  the  covmter  e.  m. 
f.  induced  and  in  part  to  the  line  voltage  itself. 
The  ratio  of  turns  on  the  first  button  of  the 
auto-transformer  may  be  10  to  1  and  on  the 
last  button  will  be  1  to  1,  which  means  that 
the  entire  line  voltage  has  been  aj^plied. 


j^UTOTRAfiTS 
FOfiMER 


^r-PSO/'—MjA 


\smmm 


circuit,  the  secondary  in  series  with  the  cir- 
cuit. Thus  the  voltage  impressed  on  the  load 
will  be  of  the  main  circuit  plus  the  amount  of 
e.m.f.  induced  in  the  secondary.  Thus,«if  the 
source  furnished  200  volts,  which  would  also 
be  the  voltage  on  the  primary  winding  of  the 

Otarjonoiy  L^minaT'ei/ 
/    A&/7  fhjmc 


>-  -  3rafionary  Cot/ 


I  Moximum 


Fig.  43. — Diagram  comparing  the  magnetic  auto- 
transformer  (left)  and  rheostatic  (right)  con- 
trols  for   x-ray  transformers.      (Cole.) 

4.  Booster  Transformer:  This  is  also  an 
alternating  current  step-down  transformer, 
consisting,  however,  of  two  separate  windings. 

i^-^ai-':     ,  .... 

Control 


Fig.  44a 


booster  and  the  secondary  was  designed  to 
deliver  20  volts,  the  e.  m.  f.  impressed  on  the 
load  would  be  220  volts  and  any  drop  of  pres- 
sure in  the  load  would  be  compensated  for  by 
inductive  action  and  thus  the  pressure  on  the 
load  kept  constant. 

y  /ton  F/^mc 


/yoMi/c   Cor^ 


■40 


JO 


Fig, 


/o,  ?o  00 

m/ummp£:r£:s  /a/ tube. 
44. — Graphic  chart  illustrating  the  comparison 
of  magnetic  auto-transformer  and  rheostatic 
control  for  x-ray  transformer  (A.  M.  Cole.)  On 
the  14th  button  there  is  a  drop  of  10,000  volts 
with  the  increase  of  the  current  from  10  to  20 
mills  under  rheostat  control  while  with  the  auto- 
transformer  control  the  drop  is  very  slight. 


(Fig.  -Wc. )  The  primary  winding  is  connected 
(parallel)    across    a    constant    voltage    in   the 


I  Zero 
Fig.  446-     (Croft.) 

There  is  another  form  of  induction  regu- 
lator so  arranged  that  the  e.  m.  f.  induced  on 
the  secondary  winding  may  be  varied  at  will. 
The  stationary  windings  are  on  a  hollow, 
cylindrical,  laminated  iron  core.  The  movable 
winding  is  mounted  on  an  iron  cylinder  within 
the  stationary  windings.     (Figs.  44a,  44b.) 

When  the  movable  coil  is  so  placed  that  all 


COIL  AXD   TRANSFORMER   DISCHARGES 


45 


tlie  flux  induced  by  the  statiimary  cuils  passes 
through  it,  the  voltage  induced  in  the  second- 
ary is  at  a  maximum.  The  movable  coil  may, 
however,  be  so  placed  that-  none  of  the  flux 
produced  by  the  stationary  coils  cuts  it  and 
no  voltage  is  induced.  Thus,  by  this  device 
the  variable  c|uantity  of  stepped-dowu  voltage 
in  the  movable  coil  may  be  added  to  the  im- 
pressed voltage. 

1 


> 


w 

.  Seco^.dLtt.iT'j'?' 

T 

Wt.wdk.vn.0    ■ 

a 

a 
o 

> 

> 

3 

o 

O 

g 

rl 

'    TrdLn$form«r  Ca.Se. 

Fig.  44f.     (Croft.) 

The  character  of  the  alternating  discharge 
from  a  coil  and  that  from  an  interrupterless 
transformer  differ  somewhat  as  shown  by  a 
study  of  the  curves.     (Figs.  46,  47,  48,  49.) 


I 


r  I 


.  pruii 


Fig.    45. — Wave    forms    of    primary    and    secondary 
currents.     (Dessaur.) 

With  the  coil,  at  the  make,  the  primary  cur- 
rent starting  from  the  neittral  point  mounts 
rapidly  in  a  positive  direction,  while  in  the 
secondary  a  negative  wave  appears.  The 
moment  the  circuit  is  broken  the  primary  wave 
falls  and  the  secondary  rises  with  great 
rapidity  and  falls  not  cjuite  as  abruptly  as  the 
primary  impulse  dmiinishes.  (Fig.  45)  This 
is  repeated  at  rapid  intervals,  the  intervals 
being  relatively  long,  as  compared  to  the  actual 
duration  of  the  wave.  The  transformer  dis- 
charge when  uncommutated  is  an  alternating 


current  wave,  the  negative  phase  being  as  long 
(Fig.  47)  or  longer  (Fig.  46)  than  the  positive 
wave.  The  rise  is  not  so  deep  and  the  fall  to 
zero  is  relatively  slow.  Commutated,  it  be- 
comes a  pulsating  current,  but  the  peaks  of  the 
coil  curves  are  higher,  (Fig.  49)  and  the  rise 
to  maximum  and  fall  to  zero  are  more  sudden. 
The  secondary  discharge,  therefore,  consists 
of  a  series  of  short  powerful  impulses,  with 
intervals  of  rest.  The  ideal  discharge  for 
energizing  an  x-ray  tube  would  be  one  having 
a  constant  potential  and  not  the  sine  wave  cur- 
rent as  developed  by  the  interrupterless  trans- 
former. 


Fig.  46. — Tracing  of  oscilligram  of  transformer  dis- 
charge. Tube  load :  100  M.A.,  41  Kv.  Useful 
voltage  above  zero  line  and  inverse  voltage  be- 
low. The  latter  is  of  higher  potential.  The 
difference  depends  on  design  of  transformer  and 
control. 

The  advantages  of  the  transformer  are  as 

follows : 

1.  The  great  amount  of  electrical  output, 
thus  permitting  the  production  of  great  quan- 
tities of  rays  and  the  examination  of  dense 
structures  in  a  fraction  of  a  second. 

2.  The  small  amount  of  primary  current 
required. 

3.  The  simplicity  in  manipulation  and  con- 
trol. 

4.  The  absence  of  inverse. 

5.  The  absence  of  interrupters. 


Fig.  47. — 25  k.w.  transformer.  Tube  load:  200  AI.A., 
70  Kv.  Upper  curve :  tube  current.  Lower 
curve:  useful  voltage  above  zero  line  and  in- 
verse voltage  below.  These  are  nearly  equal 
and  when  commutated  will  give  a  more  useful 
wave  than  a  transformer  whose  inverse  wave  has 
a  higher  potential. 


46 


CONVERTER  UNIT 


Converter  Unit  (Rieber). 
A  high  tension  transformer  has  been  con- 
structed by  Rieber,  which  he  calls  a  converter 
unit.  The  fundamental  improvement  around 
which  this  transformer  has  been  developed 
is  the  high  tension  rectifying  switch.  The 
rectifier  consists  of  a  series  of  five  rectifying 
elements  or  pole  changers,  mounted  upon  a 
common  shaft  of  bakelite,  which  runs  com- 
pletely submerged  in  oil.  The  four  collectors 
or  brushes,  which  convey  the  current  to  and 
from  each  of  these  elements,  are  of  brass  and 
make  actual  metallic  contact  with  the  phos- 
phor-bronze segments  of  the  pole  changers. 
The  principle  of  operation  diiifers  from  that 
of  the  older  types  of  rectifier ;  first,  in  that 
each  section  handles  only  one-fifth  of  the  total 
voltage;  second,  operating  under  oil  of  high 
dielectric  strength,  the  spacing  necessary  to 
prevent  flash-over  at  any  given  voltage  is 
greatl}'  reduced.    As  a  result  of  these  two  fac- 


densite  frames  having  high  mechanical  as  well 
as  dielectric  strength.  ^ 

The  synchronous  motor  which  drives  the 
rectifier  is  of  the  magnetic  cross  induction 
type.  It  has  no  commutator,  brushes  or  slid- 
ing contacts  of  any  kind,  and  hence  is  un- 
usually free  from  trouble.  Both  rectifier  and 
motor  are  mounted  vertically,  the  weight  of 
the  rectifier  shaft  being  carried  on  a  steel  on 
bronze  thrust  bearing,  while  that  of  the  motor 
armature  is  borne  by  a  double-row  self-align- 
ing ball  bearing.  The  lower  motor  bearing, 
which  carries  practically  no  load,  is  a  phos- 
phor-bronze bushing,  which  is  constantly  un- 
der the  oil  and  requires  no  attention. 

The  high-tension  transformer  consists  of  a 
core  of  non-aging  silicon  steel  and  is  of  the 
closed  type.  The  flux  density  used  is  approxi- 
mately ten  thousand  lines  per  square  centi- 
meter at  full  voltage,  which  is  about  fifty  per 
cent  of  the  saturation  point. 


Fig.  48. — Oscilligram  of  a  transformer  discharge.  ( Non-commutated)  (Hull).  In  the  interrupterless 
apparatus,  the  lower  curve  is  turned  upward.  B\'  the  use  of  a  kenotron  the  lower  curve  may  bo 
entirely  suppressed. 


fH,/^M--^/^' 


Fig.  49. — Oscilligram  of  a  coil  discharge  (coil  and  mercurj-  in.terrupter ).  The  inverse  voltage  is  shown 
below  and  the  useful  voltage  above  the  zero  line.  The  inverse  is  usually  suppressed  by  valve 
tubes.     Morton  has  devised  a  coil  apparatus  in   which   this    inverse    is    commutated   and   utilized. 

(Hull.) 


tors  the  rectifying  member  is  but  two  inches 
in  diameter  instead  of  22  to  27  inches.  It 
is  the  consequent  reduction  in  peripheral 
speed,  which  renders  possible  the  continuous 
metallic  contact,  which  is  distinctive  with  this 
machine  and  gives  it  its  freedom  from  noise, 
destructive  sparking,  and  the  evils  of  ozone 
and  nitric  acid  fumes. 

The  brushes   are   carried   in   moulded   con- 


Primary  and  secondary  coils  are  wound 
concentrically  and  so  distributed  as  to  reduce 
magnetic  leakage  to  a  minimum.  A  condensite 
barrier  tube  of  high  dielectric  strength  insu- 
lates them  from  each  other. 

The  secondary  winding  is  sectionalized  to 
correspond  to  the  rectifier,  there  being  in  effect 
five  twenty-four  thousand-volt  secondaries 
supplied  by  a  single  primary.     Each  of  these 


CONVERTER  UNIT 


47 


secondary  sections  consists  of  two  coils  wound 
in  layers  of  twenty-five  turns  each,  and  sej)- 
arated  from  each  other  by  barriers  of  moulded 
condensite.  The  coils  are  impregnated  with 
condensite  lacquer  forming  a  solid  oil-proof 
mass,  resembling  amber  both  in  appearance 
and  physical  properties.  These  secondary 
coils  are  tested  to  twice  the  maximum  work- 


ing the  high-tension  transformer,  when  the 
motor  is  at  rest,  with  a  consequent  possibility 
of  ruining  a  tube.  There  is  no  reversing 
switch  provided,  as  the  main  switch  may  be 
held  in  the  "  start  "  position  until  the  indicator 
shows  the  machine  to  be  in  phase  ( indicated 
by  a  reading  on  the  kilovolt  meter),  when  it 
is  thrown  into  the  "  run  "  position,  where  it 
catches  until  released  deliberatelv. 


Fig.    50. — Converter   unit   and   control   enclosed. 

ing  voltage  before  being  incorporated  into  the 
machine. 

The  case  or  tank  is  made  of  heavy  sheet 
steel,  riveted,  galvanized,  and  all  joints 
flooded  with  solder.  The  cover  is  cast  iron 
and  the  insulators  are  standard  high-tension 
porcelain,  bushings,  one  of  which — the  nega- 
tive— contains  the  transformer,  which  supplies 
the  current  to  the  filament  of  the  Coolidge 
tube. 

The  control  panel  contains  all  the  auxiliary 
apparatus  necessary  for  operating  the  con- 
verter, with  the  control  arranged  in  the  most 
convenient  manner  possible. 

The  switchboard  is  made  of  steel  and  is 
grounded,  and  all  operating  parts  are  con- 
cealed, making  it  impossible  to  receive  a  shock 
even  when  operating  the  machine  in  the  dark. 
The  main  switch  and  motor  switch  are  oper- 
ated by  the  same  -lever,  which  prevents  excit- 


FiG.   51.- 


-Converter   and    Control    Panel    with 
Removed. 


Case 


Tank  cover. 

Porcelain  insulators. 

Coolidge   transformer. 

Rectifier. 

High-tension   transformer. 

Cover   for  control  cabinet. 

Control  panel. 

Ballast  resistance, 
i.  Coolidge   rheostat, 
j.  Auto   transformer   switch, 
k.  Auto  transformer. 
1.  Synchronized  motor, 
r.i.  Tank, 
n.  Splitter  coil. 


48 


CONVERTER  UNIT 


The  voltage,  and  hence  the  penetration,  is 
controlled  by  the  wheel  in  the  center  of  the 
board.  With  this,  the  desired  tap  on  the  auto 
transformer  is  selected,  the  variation  being 
by  two  kilovolt  steps  and  continuous,  i.  e., 
the  voltage  may  be  changed  with  the  tube  in 
operation  without  interrupting  the  current 
even  momentarily.  This  t3'pe  of  control  in- 
sures practically  constant  penetration,  regard- 
less of  the  vacuum  of  the  tube,  a  feature  whose 
importance  cannot  be  overestimated.  The  po- 
tential once  set,  only  the  time  of  exposure 
need  be  changed  to  meet  varying  tube  con- 
ditions. 

The  switch  placed  where  most  accessible  to 
the  right  hand,  opens  automatically  when  re- 
leased. By  throwing  it  clear  to  the  left,  how- 
ever, it  catches  in  the  "  on  "  position.  Throw- 
ing it  to  the  right  throws  a  floor  push  button 
into  circuit  for  use  in  fluoroscopy. 

Immediately  in  front  of  the  voltage-control 
wheel  is  a  small  lever  by  which  resistance  in 
the  circuit  may  be  regulated.  The  first  point 
in  the  extreme  left  eliminates  all  the  resist- 
ance, giving  the  full  auto  transformer  control 
characteristics.    Point  two  inserts  a  small  pro- 


FiG.  52. — Control  panel  of  converter  unit. 

1.  Alilliammeter. 

2.  Kilovoltmeter  and  polarit\'  indicator. 

3.  Tube  regulating  switch. 

4.  Ammeter  switch. 

5.  Coolidge  control  switch. 

6.  Motor  switch. 

7.  Radio  flue  switch. 

8.  Auto  transformer  control  switch. 

9.  Ballast  resistance  switch. 

tective  or  ballast  resistance  for  treatment  work 
with  a  Coolidge  tube.  Point  three  is  intended 
primarily  for  raising  the  vacuum  of  hydrogen 
tubes.     Point  four  is  suitable  for  fluoroscopy, 


and  the  resistance  inserted  is  such  that  it  is 
impossible  to  draw  more  than  ten  milliamperes 
through  the  tube.  ^ 

The  voltmeter,  serves  both  as  an  indicator 
of  penetration  and  phase,  since  it  reads  only 
when  the  motor  is  in  step.  This  meter  is  so 
connected  into  the  circuit  that  the  voltage  to 
be  applied  to  the  tube  can  be  regulated  and 
read  before  the  tube  is  liarhted. 


Fig.  53. — ^^"iring  diagram  of  converter  unit. 

a.  Auto  transformer. 

b.  Splitter  and  switch. 

c.  Auxiliary   resistance  and  switch. 

d.  Tube  control  switch. 

e.  Coolidge  control  resistance  and  switch. 

f.  Motor  start  switch. 

g.  Ground. 

h.  Main  switch   (motor  run). 

i.  Motor  field  winding. 

j.  IMotor  starting  winding. 

k.  Coolidge   transformer  primary. 

1.  \'oltmeter  rectifier. 

m.  Ammeter  rectifier.    . 

n.  High-tension   rectifiers. 

o.  Coolidge  trar^sformer   (secondary). 

p.  High-tension  transformer  priraarj'. 

q.  Service  leads. 

A  flexible  and  sensitive  Coolidge  control  is 
built  into  the  machine,  and  is  operated  bv  the 
small  knob  immediateh'  over  the  main  switch. 
This  control  is  supplied  from  the  main  con- 
verter unit,  thus  eliminating  the  additional 
wires  so  commonly  used  when  operating  a 
Coolidge  tube  with  the  ordinary  machine.  In 
this  type  of  transformer  the  entire  sine  wave 
is  utilized. 


CHAPTER  IV 
PORTABLE  INDUCTION  APPARATUS 

\\'here  the  apparatus  is  to  be  carried  out- 
side of  the  laboratory  it  should  be  compact, 
of  small  bulk  and  suited  to  the  direct  and 
alternating  currents.  A  Tesla  coil  and  a  tube 
fitted  with  a  mechanical  interrupter  especially 
devised    for    diminishins;    inverse    is    a    use- 


Fic.  54. — Portable  coil  connected  to  storage  batteries 
with  control  box.  The  free  positive  terminal  of 
the  battery  is  connected  to  the  positive  wiring 
of  the  coil  circuit.  The  tube  stand  is  mounted 
on  the  cover  of  the  coil  box  which  also  carries 
stand  and  the  valve  tubes. 

ful  form.  In  this  apparatus,  the  alternating 
current  is  stepped  up  to  about  2000  volts.  This 
charges  a  condenser  which  discharges  at  a 
high-frequency  through  a  few  turns  of  wire 
wound  outside  a  secondary  consisting  of  many 
turns  of  fine  wire.  A  current  of  very  high 
frequency  is  thus  generated. 

\\'here  no  current  is  available,  the  ener- 
gizing current  may  be  obtained  froiu  storage 
batteries,  or  a  dynamo.  Batteries  should  be 
capable  of  delivering  twenty-four  volts  and  be 
of  at  least  thirty  ampere  hour  capacity,  pre- 
ferably of  forty-eight.  A  twelve  inch  coil  with 
heavy  primary  is  suitable  to  this  current 
and  with  a  rotary  mercury  or  a  mechan- 
ical interrupter  and  condenser  makes  an  excel- 
lent  outfit.      This    mav    be   utilized    for   field 


work,  if  the  conveniences  for  charging  are  at 
hand.  When  alternating  current  is  available, 
the  interrupter  must  be  either  mechanical  or 
a  special  form  of  electrolytic  or  mercury,  as 
described. 

The  storage  batteries  must  be  charged  by 
direct  current.  In  charging,  the  positive  ter- 
minal of  the  battery  must  be  connected  to  the 
positive  wire  of  the  charging  circuit  and  the 
negative  battery  terminal  to  the  negative  wire 
of  the  circuit. 

To  determine  the  polarity  of  the  charging 
circuit,  if  a  suitable  voltmeter  is  not  at  hand, 
dip  the  ends  of  two  wires  from  the  charging 
circuit  into  a  glass  of  water  in  which  a  tea- 
spoonful  of  salt  has  been  dissolved.  Fine  bub- 
bles of  gas  will  be  given  oft'  from  the  negative 
wire.  The  charging  rate  of  the  particular  bat- 
tery should  not  be  exceeded. 

If  only  one  battery  is  to  be  charged  from 
a  110  volt  direct  current  circuit,  resistance 
must  be  used  in  series  with  the  battery  to 
reduce  the  voltage  of  the  circuit  to  that  of  the 
battery.  The  most  convenient  resistances  to 
use  are  110  volt,  32  candle  power  carbon  fila- 
inent  lamps  connected  in  parallel  with  each 
other,  and  the  combination  in  series  with  the 
batter}'.  With  this  arrangement,  each  lamp 
will  allow  one  ampere  of  charging  current  to 
pass  through  the  battery,  so  that  the  number 
of  lamps  required  will  depend  upon  the  charge 
rate  of  the  battery.  For  instance,  if  the  charge 
rate  is  6  amperes,  six  lamps  will  be  required. 

If  32  candle  power  lamps  are  not  avail- 
able, then  double  the  number  of  16  candle 
power  lamps  will  be  required.  If  tungsten  or 
other  high  efficiency  lamps  are  used,  more  will 
be  required  than  if  carbon  filament  lamps  are 
used,  owing  to  the  lower  current  rating  of  the 
former. 

If  the  battery  is  to  be  charged  from  a  220 
volt  circuit,  use  two  lamps  in  series  in  place 
of  each  of  the  lamps  necessary  when  charg- 
ing from  110  volts. 

If  a  500  to  600  volt  circuit  is  available,  it  is 
necessary  to  use  five  lamps  in  series  in  place 


[49] 


50 


ACCU:\IULATORS 


of  each  of  the  lamps  used  when  charging  from 
110  volts. 

The  storage  batteries  may  be  charged  from 
a  dynamo  or  generator,  activated  by  a  gasoHne 
engine,  or  the  energy  may  be  obtained  di- 
rectly from  a  dynamo  (motor  generator)  con- 


FiG.  55. — Gas  engine  generating  set,  capable  of  pro- 
ducing 1000  watts,  either  in  the  form  of  14  am- 
peres and  65  volts  or  8  amperes  and  no  volts. 
The  motor  makes  800  revolutions  a  minute. 
This  is  connected  to  a  direct  current  generating 
set. 


MlUI-Jf^MCTCH f~\ 


A-/ttr  TFAnSroR/^ER- 


B0OZ7CF 


■fl^mtr  COItTPOL 


IGniTiD.v  CO/i-, 


Z0L£/,il/O 


COHMtlJATlf- 


KCS'STA'-rE 


Fig.  56. — United  States  army  portable  unit  wiring 
diagram  with  self-cooling  and  self-rectifying 
Coolidge  tube.   (Shearer)  (U.S.  Army  ^Manual.) 

nected  to  a  gas  engine.  Such  dynamos,  mak- 
ing from  800  to  1,200  revolutions,  are  capable 
of  delivering  1,000  watts  of  electrical  energy. 
This  may  be  in  the  form  of  14  amperes  at  65 
volts  or  8  amperes  at  110  volts. 


U.  S.  Army  Portable  Unit 

There  has  been  developed  for  the  United 
States  Army  service  a  portable  unit  consisting 
of  a  gasoline  engine  direct-connected  to  a 
generator  set  capable  of  supplying  both  the 
main  step-up  and  a  small  step-down  transfor- 
mer with  alternating  current  and  a  small 
amount  of  direct  current  for  the  control  cir- 
cuit. If  power  is  available  the  transformer 
part  of  the  unit  may  be  used  with  either  direct 
or  alternating  current,  the  former  by  means  of 
a  rotary  converter  being  changed  to  a  proper 
alternating  voltage.  The  secondary  circuit  con- 
tains no  recti fving  device  since  the  Coolidge 


Fig.    57. — Wiring   diagram   of    U.    S.    army   bedside 
unit  for  no  a.  c.  or  d.  c.  circuit.     (Shearer.) 

tube  for  which  the  unit  is  adapted  rectifies  its 
own  current.  The  transformer  is  capable  of 
delivering  about  57,500  volts  and  10  milliam- 
peres. 

The  gasoline  electric  set  is  a  modified  Delco, 
four-cycle,  single  cylinder,  valve-in-the-head, 
air  cooled  gas  engine,  direct-connected  to  a 
1,200  watt  a.  c.  d.  c.  generator  of  a  voltage 
varying  between  116  and  160  volts,  a.  c,  de- 
pending upon  the  speed  of  the  engine. 

Control:  The  speed  of  the  engine  and.  the 
alternating  voltage  are  varied  by  a  special 
throttle  governor,  consisting  of  a  voltage  sole- 
noid controlled  throttle,  which  regulates  the 
flow  of  fuel  in  the  cylinder  head.  This  is 
done  by  means  of  a  shutter  in  the  carburetor, 
which  is  operated  through  a  lever  by  means  of 
a  core  plunger,  which  is  drawn  up  and  down 
in  the  voltage  control  coil.  As  the  voltage 
of  the  generator  increases,  the  plunger  is 
drawn  up  and  the  shutter  decreases  the  fuel 
supply  of  the  engine.     As  the  load  increases, 


U.  S.  ARMY  L'ORTABLE  UNIT 


51 


the  throttle  opens  and  allows  more  fuel  to  pass 
into  the  cylinder  head.  The  control  coil 
plunger  is  adjusted  by  means  of  a  rheostat.  At 
a  certain  adjustment  it  is  practically  self- 
regulating. 

The  Generator:  This  is  a  shunt-wound, 
four-pole,  46  cycle,  1,400  RP:\I,  160  volt  a.  c. 
generator.  The  voltage  may  be  varied  in  steps 
from  118-volt  to  160-volt  by  means  of  a  slid- 
ing resistance  in  the  voltage  control  circuit, 
which  varies  the  speed. 

Field:  The  field  is  four-pole  and  is  excited 
from  the  d.  c.  side  of  the  armature. 

Annatiire:  The  armature  is  provided  with 
both  commutator  and  slip  rings,  so  that  a.  c. 
or  d.  c.  current  can  be  delivered. 

Oiit/^tit:  The  output  of  the  plant  is  ad- 
justed by  means  of  a  sliding  resistance  in 
series  with  the  voltage  control  circuit.  Hence, 
when  it  is  desirable  to  increase  the  amount 
of  current  to  the  x-ray  tube  and  to  the  fila- 
ment, it  is  necessary  to  speed  up  the  motor 
and  increase  the  voltage.  For  radiographic 
work  the  resistance  is  raised  until  the  line  vol- 
tage is  about  160.  Under  operating  conditions 
this  falls  to  122  volts,  if  60,000  volts  at  ten 
milliamperes  pass  through  the  tube.  For 
fluoroscopy  the  regulator  is  adjusted  until  the 
line  voltage  is  140.  Under  operating  condi- 
tions this  falls  to  122  volts,  if  60.000  volts  at 
five  milliamperes  pass  through  the  tube. 

Step-up  Transfunncr :  This  is  placed 
across  the  a.  c.  line.     It  is  oil  insulated  and  of 


the  closed-core  variety,  with  a  primary  wound 
for  the  particular  voltage.  In  the  secondary 
circuit  there  is  a  milliamperemeter.  The  leads 
for  this  meter  are  taken  from  the  grounded 
middle  of  the  transformer.  Across  the  pri- 
mary circuit  there  is  a  voltmeter,  which  indi- 
cates the  a.  c.  voltage  of  the  generator. 


Fig.  58. — U.  S.  army  portable  unit.  Both  transfor- 
mers are  in  a  case.  The  top  of  the  case  carries 
meters  and  switches. 

Step-Dozvn  Transformer:  The  step-down 
transformer  for  the  filament  current  is  of  the 
usual  type,  oil-insulated.  To  prevent  a  drop 
in  line  voltage  and  the  lowering  of  the  fila- 
ment current,  when  operating,  a  small  trans- 


Fic.  59. — The  outrit  ready  for  use.  The  engine  is  to  the  left.  The  step-up  and  step-down  transformers 
and  accessories  are  in  the  lower  part  of  the  box  at  the  end  of  the  table.  On  the  shelf  at  the  top 
are  voltmeter,  rheostat,  milliamperemeter  and  operating  switch.  The  table  is  a  portable  tro- 
choscope, the  tube  being  in  the  lead-lined  box,  which  moves  freely  under  the  bakelite  table  top. 


52 


PORTABLE  UNITS 


former,  called  a  booster  is  placed  in  the  cir- 
cuit, so  that  its  primary  is  in  the  primary  cir- 
cuit of  the  step-up  transformer  and  its  sec- 
ondary in  the  primary  circuit  of  the  Coolidge 
step-down  transformer.     When  the  switch  is 


Fig.  6o. — United  States  Arm}'  bedside  unit,  complete 
for  alternating  current  operation ;  double  throw 
switch  to  be  drawn  to  the  right,  loose  connec- 
tions below  for  rotary  converter  in  using  direct 
current. 


Fig.  6i. — Portable  horizontal  fluoroscopic  canvas- 
topped  table.  The  frame  work  is  of  steel  tub- 
ing, fitting  into  stout  wooden  ends.  The  tube 
fixed  to  underhung  ball  bearing  rollers  moves 
in  either  direction. 


closed  and  a  heavy  load  placed  on  the  genera- 
tor, the  line  voltage  will  drop,  but  by  means 
of  the  booster,  the  current  in  the  filament  is 
kept  constant.  The  heating  of  the  filament  is 
controlled  by  a  rheostat,  which  is  of  the  ad- 
justable autoflux  type. 


Fig.  62. — Standard  U.  S.  Army  x-ray  table  with 
insulating  masts  and  holders  and  box  for  stand- 
ard type  tube. 


Fig.-. 63. — Standard  U.  S.  Army  x-ray  table  complete 
with  box  for  radiator  type  tube. 

Army  X-Ray  Tabic. — The  standard  x-ray  table 
consists  of  the  following  principal  parts :  (Figs.  62 
and  63.) 

1.  Two  aluminum  end  castings. 

2.  Three  steel  side  rails. 

3.  A  rectangular  frame  as  a  tube-box  cradle. 

4.  A  lead-covered  tube  box. 

5.  A  special  detachable  shutter. 

6.  A     rectangular     wooden     frame     supporting    a 

stretcher  type  top. 

7.  An  operating  switch. 

8.  A  special  screen  carrier. 

9.  High  tension  vertical  insulators. 

10.  A  tube  holder  for  working  above  the  table. 


PORTABLE  UNITS 


55 


Fig.  65. — Mobile  x-ray  unit  (trout  view).  The  cabi- 
net is  now  fully  opened,  the  meter  and  valve 
tube  in  place  ready  lor  operation. 


Fig.  66. — Mobile  x-ray  unit — back  view. 

Figs.  64,  65.  66. 

The  three  illustrations  show  a  French  mobile 
oi)erating  unit,  devised  by  Ledoux-Lebard.  The 
total  height,  including  wheels,  is  forty-one  inches, 
width  twenty-five  inches,  depth  sixteen  inches.  The 
box  is  inounted  on  rubber  tired  wheels  and  is  divided 
into  four  compartments,  two  large  above,  one  open- 
ing from  the  front  and  one  from  the  back,  and  two 
small  ones  below.  The  lower  compartments  carry 
accessories,  screen,  gloves,  etc.  The  upper  compart- 
ment in  front  has  a  coil,  spintermetre.  and  milliani- 
peremeter.  The  rear  compartment  carries  the  inter- 
rupter which  is  so  adjusted  as  to  operate  with  either 
direct  or  alternating  current. 

An  auto  of  two  or  three  tons  capacity  may 
he  fitted  with  the  apparatus  necessary  for 
x-ray  worlc.  The  current  is  supphed  from  a 
dynamo,  mounted  on  the  chassis  under  the 
driver's'  seat,  the  dynamo  being  driven  by 
means  of  a  ckitch  arrangement  through  the 
shaft  of  the  vehicle.  This  may  be  a, 3  K.  W. 
dynamo,  having  an  output  of  twenty  amperes 
at  150  volts,  when  running  at  the  speed  of 
1,000  revolutions  per  minute.  The  photogra- 
phic dark  room  is  located  behind  the  driver's, 
seat  and  contains  sink,  rocking  bed  and  tanks. 
The  water  is  carried  in  a  reservoir  on  the  roof. 
In  the  center  is  a  compartment  which  accoin- 
modates  a  canvas  top  fluoroscope.  x-ray  tube 


54 


EQUIPMENT 


transformer,  control  stand,  etc.  A  tent,  held 
in  place  by  a  light  steel  framework  is  set  up 
for  working  purposes. 

As  a  further  development  a  standard  am- 
bulance body  has  been  modified  by  means  of 
a  few  simple  changes  so  as  to  permit  this 
body,  when  mounted  upon  a  standard  three- 
fourths  ton  chassis,  to  be  used  as  a  transport 
vehicle  for  a  complete  portable  x-ray  labora- 
tory and  equipment.  This  is  done  in  the  fol- 
lowing manner :  The  seating  arrangements 
of  the  standard  body  are  removed,  as  are  also 
the  devices  for  the  carrying  of  army  litters. 
Across  the  front  of  the  interior  of  the  body, 
tving  the  sides  together,  is  a  platform  of 
2-inch  oak  plank,  upon  which  is  securely 
bolted  the  Deko-gas-electric  set  with  its 
switchboard,  etc.  complete.  This  plank 
mounting  acts  as  a  spring  support  for  the 
engine  and  reduces  the  vibration  to  a  mini- 
mum. Stowed  away  within  the  interior  of 
the  body  in  various  dust-tight  receptacles  are 
placed  the  parts  of  the  knockdown  x-ray  table 
described  above,  the  x-ray  tube  box  with  its 
shutters,  a  portable  dark  room,  the  portable 
transformer  set,  a  bedside  unit  as  a  spare 
electrical  apparatus  and  nests  for  the  radiator 
type  of  Coolidge  tubes,  consisting  of  canvas 
hammocks,  wherein  the  tubes,  deprived  of 
their  heavy  radiators,  ride  safely.  Two  seven 
and  one-half  gallon  tanks,  one  for  water  and 
one  for  gasoline,  are  provided.  There  is  also 
provided  a  light-tight  canopy  with  a  gas-pipe 
frame  for  its  support,  which  canopy  can  be 
■erected  within  any  building  at  hand  or,  if 
necessary,  out  in  the  open,  giving  a  dark  room 
wherein  fluoroscopic  x-ray  localizations,  etc., 
may  be  performed.  On  the  sides  of  the  body 
of  the  ambulance  are  carried  three  of  the 
Avood  bakelite  table  tops  previously  referred 
to.  The  curtains  of  the  ambulance  are  longer 
than  usual  and  are  provided  with  end  flies. 
The  litter  supports  are  hinged  and  may  be 
dropped  down  to  the  horizontal,  thereby  pro- 
viding a  support  on  either  side  of  the  ambu- 
lance on  a  level  with  the  body  of  the  bed.  The 
ambulance  curtains  having  been  drawn  over 
table  tops  placed  upon  these  supports  and  the 


end  flaps  fastened  beneath  them,  there  is  pro- 
vided an  excellent  pair  of  tents  with  very 
comfortable  cots,  in  which  the  crew  of  the 
ambulance  may  sleep.  The  litter  for  the  offi- 
cer in  charge  is  placed  in  the  bed  of  the  am- 
bulance on  top  of  the  apparatus.     (Fig.  67d.) 

Equipment  for  a  Portable  Outfit 

1.  Energizing     apparatus,     interrupterless 

apparatus  or  coil  and  interrupter. 

2.  ]\Iilliamperemeter. 

3.  Tube  stand. 

4.  Protective  bowl  (lead  glass). 

5.  Compressor  cylinder. 

6.  Switchboard  and  rheostat. 

7.  X-ray  tubes. 

8.  \"alve  tube. 


Fig.  67. — \\"agon  completely  equipped  for  field  x-raj' 
work.  It  contains  dynamo,  coil,  interrupter  and 
accessories  for  radiography  or  fluoroscop\-. 

9.  Fluorescent  screen  with  protective  lead 
glass  front. 

10.  Collapsible  fluoroscope 

11.  Intensifying  screens  and  casettes  (14  x 

17).' 

12.  Negative    view    box    to    take    any    size 

negative. 

13.  Table  (canvas  topped). 

14.  Pair  of  protective  gloves — lead  rubber. 

15.  Developing  trays. 

16.  Dark  room  lamp. 

17.  Developer  and  Hypo. 

18.  One  liter  measure. 

19.  Full  set  of  connecting  cords,  heavily  in- 

sulated. 


EQUIPMENT 


55 


Aeroplane  Radiological  Unit 

A  flying  radiological  unit,  associated  with  a 
surgical  unit  has  been  devised  by  Nemirovsky 
and  Tilmant  (Figs.  6Sa,  68b,  68c).  It  aims  to 
bring  radiologic  aid  to  advanced  i)osts  without 
Roentgen  equipment.  The  aeorchir  is  designed 
to  carry,  besides  the  pilot,  a  surgeon,  a  radiol- 
ogist   and    all    the    radiological    and    surgical 


tijiixBl  Arur^ln. 


Fig.  6~b. —  Roentgen  aeroplane  unit.     Disposition  of 
parts. 


,^f,u.' -vrpttfuf    ;. 


Fig.  67a. — Roentgen   surgical  aeroplane. 

material  for  all  kinds  of  intervention.  The 
motor  of  the  plane  supplies  the  power  for  the 
Roentgen  current  with  the  interposition  of  the 
small  transformer  and  interrupter.  The  ad- 
vantages of  such  a  flying  radio-surgical  unit 
are  obvious.  The  fluoroscopic  and  radio- 
logical manipulations  may  be  done  in  the  aero- 
plane itself,  by  means  of  a  special  cap,  devised 
by  Mondain. 


Fig.  67c.- 


-Table  and  horizontal  fluoroscope  set  up  for 
operation — aeroplane   unit. 


Fig.  67d.    .American  Camion  with  Engine  Mounted  behind  Driver's  Seat 
(."Kmer.  Jour  of   Roentgenology.) 


CHAPTER  V 
THE  DISCOVERY  OF  THE  X-RAY 

The  researches  which  eventually  led  to  the 
discovery  of  the  x-ray,  began  with  the  ex- 
periments of  Faraday,  who  in  1837  studied 
the  effects  and  nature  of  electric  discharges 
in  air  and  in  various  gases. 

At  atmospheric  pressure,  he  found  the 
color  of  the  discharge  to  be  purple :  when  the 
air  was  somewhat  rarefied,  a  deeper  purple, 
gradually  shading  to  a  beautiful  rose  color. 
In  oxygen,  at  atmospheric  pressure,  the  color 
was  a  dull  white,  but  when  rarefied,  purple. 
With  hydrogen  it  was  of  a  greenish  gray. 
With  nitrogen  there  was  a  magnificent  display 
of  a  variety  of  colors.  In  all  these  experi- 
ments these  luminous  eft'ects  were  visible  at 
the  anode  end.  He  found  that,  whereas  at 
ordinary  pressure  the  glow  was  most  marked 
at  one  pole,  when  the  atmosphere  or  gas  was 
rarefied,  the  glow  changed  into  striae  or 
stripes  of  varying  color,  which  moved  in  rings 
from  anode  to  cathode. 

In  all  these  experiments  and  the  experi- 
ments of  those  who  came  after  him,  it  was 
the  glow  discharges  and  striae,  originating  ap- 
parently at  the  anode,  which  were  studied.  It 
was  only  when  the  rarefication  of  the  atmos- 
phere within  the  tubes  was  greatly  increased 
and  the  luminous  eft'ects  at  the  anode  end 
began  to  disappear,  that  the  attention  of 
physicists  was  directed  to  the  negative  or 
cathode.  Experiments  along  this  line  resulted 
finally  in  the  production  of  the  x-ray. 

The  first  step  towards  this  end  was  made 
by  Plucker,  who  engaged  Geissler  in  1869  to 
blow  for  him  a  glass  tube  in  which  platinum 
wire  electrodes  were  sealed  in  the  glass  by 
fusion,  as  in  the  modern  incandescent  lamp. 
The  air  was  exhausted  by  a  mechanical  air 
pump,  through  a  capillary  tube,  which  was 
finally  sealed.  This  was  the  first  attempt  to 
make  a  tube  in  which  a  permanent  vacuum 
could  be  maintained.  Geissler  was  enabled 
to   produce    luminous    colors   by    rubbing   the 

[56] 


outside  of  the  tube.  In  other  words  he  sHbwed 
that  the  matter  within  could  be  made  radiant 
by  means  of  an  electric  charge  applied  from 
without. 

Plucker,  however,  charged  these  tubes  with 
electric  current  and  found  that  beautiful 
luminous  effects  could  be  produced,  which 
persisted  if  the  vacuum  of  the  tube  was  raised 
but  that  then  Geissler's  experiment  of  pro- 
ducing colors  by  rubbing  the  tube  could  no 
longer  be  performed. 

Carrying  this  principle  still  further,  Mor- 
gan in  1875  exhausted  the  tube  still  more  and 
found  that  when  a  high  state  of  vacuum  ex- 
isted no  electro-motive  force  could  drive  a 
spark  from  one  terminal  to  the  other,  no 
matter  how  close  together  these  were. 

Plucker,  in  producing  the  luminous  effects 
in  the  tube,  which  he  had  constructed,  found 
that  striae  and  luminous  colors  produced  at 
the  cathode  end  could  be  deflected  by  a  magnet 
and  made  to  strike  the  side  of  the  bulb.  The 
experimental  work  on  these  striae  received 
great  stimulus  by  the  improvement  of 
energizing  apparatus  through  the  discovery 
of  the  method  of  producing  powerful  currents 
of  high  electromotive  force  based  on  the  prin- 
ciple of  magnetic  induction.  It  was  not  long, 
therefore,  before  a  Geissler  tube  was  intro- 
duced into  such  a  circuit  by  Moore. 

In  1879  Crookes  published  some  of  his  ex- 
periments with  the  Geissler  tubes  and  power- 
ful currents.  He  modified  the  original  Geiss- 
ler tube  by  inserting  a  third  pole  in  the  center 
of  the  tube,  which  he  made  the  cathode,  while 
the  two  terminals  at  either  end  were  connected 
together  and  made  the  anode.  Upon  operat- 
ing such  a  tube,  by  means  of  these  .powerful 
currents,  he  found  that  a  dark  space  was 
present  for  about  one  inch  on  both  sides  of  the 
negative  plate.  Beyond  that  point  however 
there  were  numerous  and  beautiful  striae  and 
the  tube  was  extremely  phosphorescent. 

It  must  be  remembered  that  in  all  his  ex- 
periments Crookes  was  interested  in  the  phe- 
nomenon occurring  within  the  tube  about  the 


CROOKES'  EXPERIMENTS 


57 


anode,  and  the  phosiihorescence  of  certain 
chemicals  when  placed  within  the  tube.  He  as 
yet  did  not  suspect  that  etTects  could  be  pro- 
duced outside  of  the  tube.  He  introduced  jew- 
els within  the  tube  and  noted  their  phosphores- 
cence. He  then  attempted  to  raise  the  vacuum 
to  a  high  degree  and  found  that  at  a  point  di- 
rectly opposite  the  dark  cathode  end  there  was 
a  patch  of  green  light  on  the  inner  surface  of 
the  glass, — that  this  patch  appeared  no  mat- 
ter where  the  anode  was  placed.  He  found 
too  that  a  piece  of  metal  inserted  m  the  path 
of  this  beam  cast  a  shadow  on  the  glass.  He 
decided  that  this  beam  consisted  of  a  radia- 
tion of  highly  attenuated  particles  moving  in 
a  molecular  stream  across  the  tube,  for  a  little 
wheel  inserted  in  its  path  could  be  made  to 
move.  This  molecular  stream  or  discharge, 
which  apparently  originated  at  the  negative 
end  and  traveled  with  tremendous  velocity,  he 
called  a  cathode  stream.  He  found  that  this 
stream  could  be  deflected  by  a  magnet. 

The  next  step  was  to  make  the  cathode 
pole  concave,  so  as  to  focus  this  stream  to  a 
point.  He  found  that  this  could  be  done  but 
that  considerable  heat  was  developed  at  the 
focal   point   and   the   heat   cracked   the   glass. 


Fig.  68. — Crookes'   Experiment. 

He  little  knew  in  making  this  experiment  that 
the  green  phosphorescence  at  the  point  of  the 
focus  of  the  cathode  stream  was  the  source  of 
x-rays.  Seventeen  years  elapsed  between  the 
experiment  of  Crookes  and  the  experiments  of 
Lenard  and  Roentgen.    In  1892  Hertz  made  a 


contribution  to  this  line  of  research  which  then 
seemed  of  trival  importance  but  which  fore- 
shadowed the  discovery  of  Roentgen.  He  in- 
serted a  piece  of  uranium  glass,  covered  on 
one  side  with  gold  leaf  and  mica,  into  a 
vacuum  or  Crookes'  tube,  and  found  that  after 
he   had   produced   enough    exhaustion    of    air 


Fig.  69. — Lenard  Tube  with  aluminum  window.  K 
metal  cap  over  one  end  of  the  tube  in  which  is 
fitted  L,  aluminum  window.  C  is  the  aluminum 
cathode.     A,   the  cylindrical  anode. 

within  the  tube  and  genuine  cathode  rays 
struck  the  covered  glass — then  phosphores- 
cence manifested  itself  on  the  glass  behind 
the  gold  leaf.  As  the  exhaustion  of  the  tube 
was  continued  and  the  cathode  rays  were 
fully  developed,  the  gold  leaf  hardly  had  any 
effect  at  all  in  preventing  the  passage  of  the 
cathode  stream  to  the  glass  while  the  mica 
cast  deep  shadows.  He  tried  the  same  ex- 
periment by  putting  silver  leaf,  alimiinum, 
etc.,  within  the  bulb  but  these  apparently  had 
no  effect  in  withholding  the  passage  of  the 
cathode  stream.  He,  therefore,  concluded  that 
the  pure  cathode  stream  could  pass  through 
metal  substances  and  tn^anium  glass  and  he 
now  suggested  that  the  attention  of  the  physi- 
cists be  turned  to  what  occurs  outside  of  the 
walls  of  the  tube,  since  this  cathode  stream 
could  pass  through  it. 

Hertz  died  and  his  pupil,  Lenard,  enthusi- 
astically took  up  the  work  along  the  line 
suggested  by  his  master.  His  investigations 
were  the  last  steps  before  the  discovery  of  the 
x-ray.  He  confined  his  entire  attention  to  the 
effect  of  the  cathode  stream  as  it  penetrates 
through   the   tube   into   the   atmosphere.      He 


58 


LENARD'S  EXPERIMENTS 


used  a  tube  with  a  small  aluminum  window 
against  which  the  cathode  stream  was  directed. 
Lenard  now  found  that  this  cathode  stream, 
or  the  cathode  rays,  were  propagated  in  the 
open  air.  He  studied  their  properties  and 
found  that  they  could  cause  phosphorescence 
of  certain  substances,  as  uranium,  etc.,  but  that 
this  effect  was  diminished  if  the  stream  was 
first  permitted  to  pass  through  the  glass  or  tin 
foil. 

He  found  that  this  phosphorescence  would 
cease  if  a  magnet  were  applied  to  drive  the 
cathode  stream  away  from  the  point  at  which 
it  was  directed.  He  found  too  that  the  cath- 
ode stream  would  penetrate  certain  substances 
outside  of  the  tube  and  that  it  had  photo- 
graphic action.  He  studied  this  external 
cathode  ray  and  compared  its  effect  to  those 
of  sunlight.  He  found  too  that  the  higher  the 
vacuum,  the  more  powerfully  penetrative  were 
these  external  cathode  rays.  Undoubtedly  he 
too  was  working  with  x-rays,  but  did  not  ap- 
preciate this,  although  he  recognized  that  there 
were  several  kinds  of  cathode  rays  which  dif- 
fered in  their  penetrative  power. 

Roentgen  experimented  with  these  newly 
discovered  rays. 

*  During  one  of  these  experiments  on  being 
called  from  the  room,  he  laid  the  still  glow- 
ing bulb  on  a  book  he  had  been  reading  that 
morning,  in  which  lay  a  large,  flat,  antique 
key,  which  it  was  his  wont  to  use  as  a  book- 
mark. It  happened  that  underneath  this  book 
lay  a  photographic  plate  holder  which  he  had 
prepared  for  an  afternoon's  outing.  Return- 
ing later  to  the  laboratory,  he  gathered  up 
several  plate  holders,  among  which  was  the 
fateful  one  under  the  book,  and  spent  the 
afternoon  outdoors,  seeking  recreation  and 
amusement  in  the  practice  of  his  hobby,  pho- 
tography. He  made  several  exposures.  On 
developing  the  plates,  a  shadow  of  the  antique 
key,  his  bookmark,  appeared  on  one  of  them. 
He  wondered  how  this  could  have  happened. 
He  showed  the  plate  to  his  students  and  asked 
them  for  their  ideas,  but  none  of  the  explana- 


*  From  a  biographical  sketch  of  W.  C.  Roentgen 
N.  Y.  Aled.  Jour.  Dec.  25,  '15  by  I.  S.  Hirsch. 


tions  offered  satisfied  him.  How  came  the 
image  of  the  key  upon  the  plate?  The  fog- 
ging of  photographic  plates  in  the  proximity 
of  energized  vacuum  tubes  had  been  noted 
before,  but  to  Roentgen's  scientific  mind  this 
phenomenon  demanded  a  satisfactory  explana- 
tion and  he  proceeded  to  analyze  it  . 

Hertz  had  said  that  something  passed 
through  the  walls  of  the  tube.  But  these  were 
cathode  radiations  from  the  Lenard  tube, 
which  Lenard  had  so  thoroughly  studied.  It 
was  known  that  these  cathode  rays,  when 
brought  through  the  aluminum  window  of  a 
vacuum  tube,  moved  in  straight  lines,  dis- 
charged electrified  bodies,  penetrated  thin  sub- 
stances, and  aft'ected  photographic  plates.  But 
this  was  no  Lenard  tube  with  an  aluminum 
window,  but  a  relatively  highly  exhausted 
Crookes'  tube,  and  neither  cathode  rays  nor 
ultraviolet  light  could  pass  through  the  glass 
of  the  tube  and  accomplish  this.  Roentgen 
decided  therefore  to  search  for  the  mysterious 
agent  which  had  so  silently  recorded  its  pres- 
ence. He  restaged  the  drama,  placing  the 
glowing  bulb,  the  tube,  the  book,  the  key,  and 
plate  exactly  as  before,  and  energized  the 
tube  for  the  same  time  as  on  the  preceding 
day.  He  developed  the  plate  and  Lo !  the 
shadow  picture  of  the  key  was  on  the  plate. 
Invisible  light?  \\'as  some  influence  emanat- 
ing from  the  glowing  bulb  that  had  the  power 
of  penetrating  solid  objects  and  affecting  the 
photographic  plate  ? 

Noting  the  green  fluorescence  of  the  glass 
of  the  Crookes'  tube,  he  conceived  that  other 
substances  might  be  similarly  aff'ected.  He, 
therefore,  surrounded  the  tube  with  a  light 
proof  envelope,  and  sure  enough,  a  platinoba- 
rium  cyanide  screen,  even  at  a  distance  of  nine 
feet,  fluoresced  brilliantly  green  in  the  dark- 
ened room.  Eureka !  He  had  it — a  ray  in- 
visible to  the  eye  which  traversed  solid  sub- 
stance. He  placed  his  hand  on  a  covered  pho- 
tographic plate,  energized  the  Crookes'  tube 
above  it,  and  obtained  a  photograph  of  the 
shadows  of  the  bones. 

He  then  subjected  these  rays  to  very  strong 


ROENTGEN'S  DISCOVERY 


59 


magnetic  fields,  they  could  not  be  deflected 
and  they  differed  in  several  other  characteris- 
tics from  the  cathode  stream  of  Lenard. 
These  mysterious  rays  he  called  the  x-rays. 
He  found  that  the  rays  had  considerable  pen- 
etrative power,  and  that  after  they  had  pen- 
etrated through  so-called  opaque  objects,  for 
instance  the  pages  of  a  book — they  still  could 
afl^ect  fluorescent  substances  and  darken  pho- 
tographic films.  The  x-rays  were  not  visible  to 
the  retina  and  in  order  to  make  them  visible  he 
made  use  of  the  property  that  the  ray  has  of 


causing  certain  chemical  substances  such  as 
platino-barium  cyanide  to  fluoresce. 

He  then  performed  the  experiment  of  hold- 
ing his  hand  between  the  screen  and  the  tube 
and  beholding  a  shadow  picture  of  the  bones 
of  his  hand. 

This  was  a  contribution  of  inestimable 
worth  to  science.  To  medicine  it  gave  a  new 
method  of  examination.  In  physics,  it  initi- 
ated a  series  of  researches  which  are  destined 
to  revolutionize  the  preconceived  notions  of 
the  constitution  of  matter. 


CHAPTER  VI 

THE  CROOKES'  OR  GAS  TUBES 

The  development  of  the  x-ray  tube  to  its 
latest  type  has  become  possible  through  the 
improvement  of  the  methods  of  its  exhaus- 
tion. The  "Molecular  Pump"  of  Gaede  was 
a   distinct  advance  over  the  mechanical  methods 


Fig.  70. — Various  forms  of  x-ray  tubes. 

I,  2, — type  of  tube  used  by  Roentgen. 
3,  4, — type  of  tube  used  by  Jackson. 
5, — double  target  tube. 
6-10, — modern  types  of  tubes. 

previously  used,  but  the  best  form  of  exhaus- 
tion apparatus  was  described  by  Gaede  in 
1915.  It  utilizes  a  column  of  mercury  vapor 
produced  by  boiling  mercury.  This  column  of 
vapor  passes  by  a  narrow  slit  which  communi- 
cates with  the  chamber  to  be  exhausted  and 
carries  away  its  gas  molecules  to  a  container 
from  which  the  air  is  drawn  by  mechanical 
means.  During  exhaustion  the  glass  of  the 
bulb  is  maintained  at  a  high  temperature  in 
order  to  free  it  of  all  occluded  and  adherent 
foreign  gases.  The  heating  of  the  anode  is 
maintained  by  energization.  In  the  exhaus- 
tion of  a  bulb,  no  eitects  are  observed  until 
the  pressure  falls  below  1/60  of  an  atmos- 
phere.     A    faint    glow    then   becomes    visible 


near     the     terminals.       As     the     exhaustion 
continues,  long  threads  of  light  are  seen  ex- 
tending between  the  terminals  and  these  com- 
bine until  they  form    (at  one-twelfth  atmos- 
pheric  pressure)    a    luminous    reddish   violet 
column,    which    extends    from    the    anode    to 
within  a  short  distance  of  the  cathode.     This 
is     known     as     the     positive     column.     The 
cathode  is  surrounded  by  a  bluish  glow  known  ' 
as   the   cathode   glow   and  is   separated   from 
the  positive  column  by  a  non-luminous  space 
known   as   the   Faraday   dark-space.     As   the 
pressure   falls  the  cathode  glow  increases  in 
brilliancy    and    the    dark    space    increases    in 
extent  and  the  positive  column  is  broken  up 
into  violet  or  reddish  colored  striae  or  rings, 
which   have   their   concave   side   towards   the 
anode.     The  walls  of  the  tube  fluoresce  with 
a  greenish  light.     At  this  time  about  1/700  of 
the  air  is  left  in  the  tube.     The  negative  glow 
now  becomes  separated  from  the  cathode  by 
a  sharplv  defined,  non-luminous  space,  known 
as  Crookes'  dark-space.     As  exhaustion  pro- 
ceeds, this  space  increases  in  extent  ( the  glow 
and  the   striae   receding   to   the   positive   end 
and   growing    fainter    until    they    disappear). 
The  new  violet  glow,  called  the  positive  glow 
is  now  seen  about  the  target,  while  the  bluish 
violet  cathode  stream  extends  from  the  cathode 
to  the  target.     At  an  exhaustion  of  1/100000 


Fig.  "I. — Roentgen's  Experiment.  C  is  the  cathode 
from  which  the  cathode  stream  is  emitted  in 
straight  lines  to  the  glass  of  the  bulb— generat- 
ing x-rays  which  radiate  irregularly  in  all  direc- 
tions. 

of  an  atmosphere,  .001  ni.  m.  pressure  of  mer- 
cury,   a   yellowish   green,    (due   to   the    man- 


[60] 


ROENTGEN'S  X-RAV  TUBE 


61 


ganese  in  tubes  made  of  soda  glass )  or  blue 
(in  tubes  of  lead  or  lithium  glass)  fluorescence 
of  the  glass  appears  opposite  the  anode.  This 
fluorescence  is  not  due  to  x-rays  but  to  the 
impact  of  the  reflected  cathode  rays  from  the 
target. 

The  tube  used  by  Crookes  consisted  of  a 
cylindrical  bulb  (  Fig.  68A  ),  twenty-five  centi- 
meters long  and  six  centimeters  wide,  in  both 
ends  of  which  were  fused  wire  electrodes. 
These  were  connected  to  each  other  and  con- 
stituted the  anode.  Between  them,  in  the  mid- 
dle of  the  bulb  a  wire  was  inserted,  which 
served  as  the  cathode.  Towards  the  negative 
end  there  was  an  extension  which  was  con- 
nected to  a  pump,  by  which  the  vacuum  was 
produced.  It  was  with  this  tube  that  he,  dis- 
covered the  dark  space  about  the  cathode. 
Later  he  worked  with  a  V-shaped  tube  (Fig. 
68),  one  end  of  the  Y  being  anode  and  the 
other  cathode,  and  found  that  the  cathode  end 
was  always  luminous  and  the  anode  dark. 

The  tube  used  by  Lenard  was  one  of 
the  type  shown  in  Fig.  69.  It  was  perma- 
nently connected  to  the  vacuum  pump.  The 
cathode  consisted  of  a  thin  disc  of  aluminum. 
Over  one  end  of  the  tube  was  a  metal  cap, 
having  a  window  of  a  thin  sheet  of  aluminum. 
The  anode  was  a  heavy  brass  cylinder  sur- 
rounding the  wire  of  the  cathode. 


Fig.  72. — The  signs  indicate  the  distribution  of  the 
electric  charge  on  the  surface  of  the  tube.  N.  S. 
=:  neutral  space.     R  =  regulator. 

The  anode  and  aluminum  window  were  con- 
nected and  grounded.  It  was  with  this  tube 
that  he  studied  the  properties  of  the  cathode 
rays,  as  they  passed  through  the  aluminum 
window. 

The  type  of  tube  used  by  Roentgen  was  a 
pear-shaped  bulb;  having  a  diameter  of  three 


to  four  centimeters  and  a  length  of  twenty  to 
thirty  centimeters  (Figs.  70-1).  in  which  two 
aluminum  electrodes  were  fused  in  the  glass 
b}'  means  of  platinum  connections. 

The   cathode    consisted    of    an    alummum 
plate  of  such  size  as  to  occupy  the  entire  trans- 


FiG.  73. — In  the  modern  tube  the  cathode  stream  is 
made  to  converge  upon  the  target  F  to  a  very 
small  area — called  the  focal  area  or  focus  spots. 
A^Anode.      C — Cathode.    B — Accessory    anode. 


verse  section  of  the  tube.  The  anode  consisted 
of  a  ring  of  aluminum  wire,  placed  in  a  small 
depression  in  the  bulb. 

Such  a  tube,  when  energized,  resulted  in 
the  formation  of  the  cathode  stream,  which 
radiating  from  the  cathode  at  right  angles  to 
its  surface,  struck  the  glass,  producing  a  bril- 
liant fluorescence. 

By  making  the  cathode  concave,  instead  of 
flat,  it  was  found  that  the  stream  could  be 
brought  to  a  focus.  But  the  enormous  heat 
generated  at  the  point  of  impact  of  the  stream 
melted  the  glass  and  destroyed  the  tube.  The 
next  step,  then,  was  to  insert  a  thin  sheet  of 
metal,  the  so-called  anticathode  or  target,  upon 


62 


PLAN  OF  X-RAY  TUBE 


which  the  stream  was  directed.  This  was  now 
the  positive  pole  of  the  tuhe. 

It  was  now  found,  however,  that  the  rays 
were  directed  back  to  the  cathode  end  of  the 
tube  and  to  obviate  this  the  metal  plate  was 
tilted  at  an  angle  of  forty-five  degrees,  accord- 
ing to  a  suggestion  in  his  first  paper. 

Before  the  publication  of  Roentgen's  second 
paper,  March  9,  1896,  an  exactly  similar  tube 
to  the  one  he  used  for  the  majority  of  his  later 
experiments,  was  described  by  Jackson.  The 
cathode  was  of  aluminum  and  concave,  the  an- 
ode of  platinum,  tilted  at  an  angle  (Figs.  70-6). 

The  great  heat  generated  at  the  anode  af- 
fected the  metal  parts  and  the  glass  wall  of 
the  tube.  For  this  reason  a  bulb,  instead  of 
a  cylindrical  tube,  was  adopted. 

Platinum  is  used  for  the  fixation  of  the 
electrodes  in  the  glass,  because  it  has  the  same 
heat  expansion  coefficient  as  glass.  The 
anticathode  must  be  of  such  a  metal  as  has 
a  high  atomic  weight,  a  high  melting  point, 
and  be  capable  of  considerable  heating  with- 
out disintegration.  Its  construction  and  posi- 
tion in  the  bulb  should  be  such  as  to  permit 
rapid  radiation  of  heat  and  to  give  absolute 
immobility.   This  makes  sharp  focusing  of  the 


Fig.   74. — A  double  target    (stereoscopic)    tube  with 
air  cooling  device   (radiator). 

cathode  possible.     Platinum,  tantalum,  iridium 
and  tungsten  are  the  metals  used. 

By  improvement  in  pumping  methods,  the 
penetration  of  the  rays  emitted  was  increased. 
The  exhaustion  of  the  modern  tube  leaves 
less  than  1/1,000,000  of  an  atmosphere.     The 


gas,  which  adheres  to  the  walls  of  the  tube  and 
the  electrodes,  is  removed  by  heating  from  the 
outside,  the  tube  being  energized  while»-it  is 
being  exhausted. 

The   plan   of    construction    of    the    modern 
x-ray  tube  is  indicated  in  Fig.  7i.     The  tube 


Fig.  75. — Water-cooled  tube. 

is  a  spherical  bulb  with  several  cylindrical 
projections.  This  bulb  is  from  twelve  to 
twenty-two  centimeters  in  diameter.  It  is 
exhausted  to  the  pressure  of  at  least  .001  milli- 
meters of  mercury.  The  concave  cathode  of 
aluminum  is  placed  into  one  of  the  glass  pro- 
jections, slightly  below  the  level  of  the  inner 
curvature  of  the  bulb.  The  curvature  of  the 
cathode  is  from  eighteen  to  twenty-two  diop- 
ters. 

The  anticathode  or  target  is  generally 
placed  at  an  angle  of  forty-five  degrees  to  the 
direction  of  the  cathode  stream,  almost  in  the 
center  of  the  bulb  and  beyond  the  geometrical 
focus  of  the  cathode. 

The  relationship  between  cathode  and  tar- 
get is  very  important  and  determines  not  only 
the  size,  shape  and  position  of  the  focus 
point  (which  is  the  point  of  impact  of  the 
cathode  stream  on  the  target),  but  the  steadi- 
ness and  quality  of  the  ray  emission. 

The  so-called  accessory  anode  is  used  in 
place  of  the  anticathode  in  the  pumping  of 
the  tube,  in  order  to  avoid  a  disintegration  of 
the  target.  When  the  tube  is  used  this  and 
the  target  are  connected  and  serve  as  anode. 
Besides  this  there  is  a  small  accessory  cham- 
ber which  contains  the  device  for  regulating 
the  vacuum  of  the  tube. 

The  changes  in  tube  architecture  along  the 


VARIETIES  OF  GAS  TUBES 


63 


lines  of  anodal  construction,  methods  of  cool-  radiating   element.      Though    platinum    has    a 

ing  and  vacuum  regulation  have  given  rise  to  higher  atomic  weight  than  tungsten,  195.2  to 

a    number   of    variations    from    the    standard  184  and  the  amount  of  tungsten  radiation  is 

above  described.  only  91%  of  platinum  still  tungsten  is  the  pre- 


FiG.  76. 

Figs,  yd,  77,  78. — Types  of  double-walled  oil  cooled 
tubes.     (Hirsch.) 

I.  The  variations  in  the  slioj^c  and  consti- 
tution of  the  target  haz'c  produced  sci'cral 
types  of  tubes. 

The  requisites,  which  a  target  in  a  modern 
tube  should,  according  to  Kaye,  possess,  are : 

1.  High  atomic  weight — to  secure  a  large 
quantity  of  rays. 

The  fraction  of  cathode  rays  converted  into 
jc-rays  increases  with  the  atomic  weight  of  the 


Fig.  77. 

ferred   element   because   its    melting   point   is 
above  3000  while  that  of  platinum  is  1760. 

2.  High  melting  point — to  permit  sharp 
focusing  without  melting  of  target. 

3.  High  heat  conductivity — to  minimize  the 
heat  production. 

4.  Low  vapor  pressure  at  high  temperature 
— to  avoid  sputtering  and  disintegration  of  the 
target  on  the  walls  of  the  tube. 

The  target  may  be  a  disc  of  pure  platinum, 
platinum  coated  nickel  or  copper,  pure  tung- 


64 


AXODAL  COXSTRUCTIOX 


sten  iridium,  or  buttons  of  these  metals 
set  in  copper  or  iron  heads.  Copper  has  three 
times  the  heat  conductivity  of  tungsten  and 
aids  therefore  considerably  in  carrying  off 
the  heat  from  the  target.  The  coating  of 
platinum  need  only  be  very  thin.     The  target 


Fig.  78. 

Fig.  78. — The  X-ray  bulb  of  oval  shape  is  surrounded 
by  an  oval  sleeve  of  lead  glass  with  an  opening 
in  front,  over  which  a  filter  may  be  placed. 


is  usually  flat  but  a  curved  target  consisting 
of  a  copper  head  covered  with  a  thin  layer  of 
platinum  has  been  produced.  The  target  and 
its  stem  in  some  continental  types  is  sur- 
rounded by  a  glass  sleeve  for  the  purpose  of 
diminishing  the  effects  of  inverse  discharges. 
The  iron  sleeve,  carrying  the  target  may  be 
extended  and  bear  various  forms  of  radiating 
devices  to  carry  oft'  the  heat. 

The  Stereo  Tube 

In  the  stereo  tube,  Fig.  74,  there  are  two 
cathodes,  both  of  which  are  connected  to  the 
negative  pole,  and  a  double  target,  which  is 
the  anode.  The  focal  points  on  the  targets 
should  be  six  centimeters  from  each  other. 
By  reversing  the  ciu-rent  after  one  of  the  ex- 
posures, another  exposure  is  made  similar  to 
that  obtained  when  an  ordinary  tube  is  shifted 
a  distance  of  six  centimeters. 


II.  Tlic  zvriatious  in  inctliods  of  cooling 
have  resulted  in  the  production  of  several 
types  of  tubes.  ^ 

The  \\'ater-Cooled  Tube 

In  this  tube  the  target  is  cooled  by  water 
(Fig.  75").  The  tai-get  forms  the  bottom  of 
a  small  metal  cup  which  is  fixed  to  a  glass 
sleeve  provided  with  an  expanded  portion 
which  acts  as  a  reservoir.  Those  models 
are  best  in  which  the  target,  consisting 
of  platinum,  forms  the  floor  of  the  water  con- 
tainer. They  are  of  value  when  continued 
usage  over  long  periods  is  necessary,  as  in 
fluoroscopy  or  therapy.  A  modification  of- 
this  tube,  wherein,  instead  of  a  reservoir,  a 
spray  of  water  is  maintained  against  the  target 
has  had  its  vogue. 

The  Oil-Cooled  Tube 
In  this  tube  the  x-ray  bulb  is  enclosed  by 
an  enveloping  chamber  into  which  oil  is 
placed ;  this  oil,  by  cooling  the  anode  and  cath- 
ode and  glass  bulb,  maintains  the  vacuum  at  a 
constant  point.   At  the  same  time  the  oil  in  the 


Fig.  79. — Air-cooled  target  with  radiator. 


COOLING   METHODS 


65 


enveloping  chamber  filters  the  very  softest 
rays.  The  x-ray  tube  itself  is  equivalent  to  a 
15-cm.  bulb,  and  is  of  oval  form,  permitting 
the  target  to  be  placed  in  close  proximity  to 
the  body. 

The  window  through  which  the  oil  is  poured 
is  closed  by  caps  made  of  different  materials 
for  filtration.  The  enveloping  glass  shield 
may  be  of  lead  glass. 

The  Air-Cooled  Tube 

Air  is  forced  by  means  of  a  pressure  pump 
through  inlet  tubes  set  in  the  hollow  cathode 
and  target.  The  latter  is  massive  and  of  cop- 
per. The  tungsten  button  is  set  into  it,  so 
that  it  forms  the  floor  of  the  hollow  stem. 
The  effective  cooling  of  the  cathode  prevents 
the  progressive  hardening  of  the  tube. 

III.  Tlic  rariatioiis  in  iiicthods  of  reduc- 
ing or  raising  the  vacuum  have  produced 
several  types  of  tubes.  There  are  four 
methods  for  maintaining  the  desired  working 
vacimm. 


Fic.  80. — .\ir-regfulating  device.  The  mercury  is 
shown  in  the  curved  tube  (b),  the  porous  mem- 
ber is  at  P  and  (f)  is  the  filter.  When  the 
mercury  is  forced  away  from  this  chamber  a 
molecule  of  air -enters  the  bulb. 


1.  By  obtaining  a  cycle  of  events  through 
catalytic  action. 

2.  By  obtaining  a  cycle  by  evaporation  and 
condensation.  Mercury  is  the  only  element 
that  can  be  used  in  this  way. 

3.  By  re-supplying  the  necessary  gases  auto- 
matically by  the  action  of  heat  on  suitable  sub- 
stances. 

4.  By  automatically  feeding  gas  (hydrogen 
or  air)  to  the  tube  by  means  of  a  valve. 

The  osmo-regulator  was  one  of  the  earliest 
devices  utilized.  A  thin  palladium  tube  is 
fused  into  the  side  of  the  bulb.  Palladium 
has  the  propertv  of  absorbing  hydrogen,  when 
heated.  An  alcohol  flame  (which  contains 
I 


iH-^^ 


Fig.  81. — Hydrogen  tube. 

much  hydrogen)  is  used.  The  palladium  tube 
thus  saturated  with  hydrogen  delivers  a  part 
of  it  into  the  tube  lowering  the  vacuum.  It 
does  not  permit  the  passage  of  other  gases. 

]\Iica.  carbon  and  potassium  hydroxide 
have,  when  heated,  the  property  of  giving  off 
gas  or  vapor. 

The  former  two  are  placed  in  the  accessory 
chamber  in  the  form  of  small  discs,  the  latter 
is  mixed  with  asbestos  shavings  and  is  tightly 
packed  into  the  bottom  of  the  chamber.  These 
are  heated  by  shunting  the  secondary  into 
the  regulating  chamber,  by  means  of  a  hinged 
wire  which  may  be  brought  into  the  proximity 
of  the  cathode  end  of  the  tube.  The  regula- 
tion may  be  accomplished  automatically. 
When  the  resistance  in  the  tube  becomes  too 
high,  the  discharge  passes  across  the  alter- 
native gap  between  the  hinged  wire  of  the 
regulator  and  cathode. 

Another  class  of  air  regenerating  devices  is 
the  "  air  or  gas  regulator."  In  an  accessory 
chamber  filled  with  hydrogen  or  air  there  is  a 
small  u-formed  tube,  filled  with  mercury,  in 


66 


REGENERATING  DEVICES 


the  wall  of  which  a  piece  of  porous  sub- 
stance (carbon),  the  size  of  the  head  of  a  pin 
is  placed.  This  is  impenetrable  to  mercury 
but  penetrable  to  gas.  ^^'hen,  through  pres- 
sure, the  mercury  is  displaced  from  the 
porous  piece,  the  gas  from  the  chamber  or  a 
molecule  of  air  enters  through  the  carbon  into 
the  tube.  These  regulating  devices  are  ver\- 
valuable  for  fluoroscopy  but  not  for 
radiography. 

In  another  variety  of  tubes  the  reduction  of 
the  vacuum  is  accomplished  by  the  admission 
of  h3fdrogen  from  an  accessory  chamber  into 
the  bulb  when  an  osmotic  metal  located  in 
the  septum  is  heated.  The  chamber  contains 
enough  gas  to  regulate  the  tube  1500  times. 
The  osmotic  member  is  heated  to  redness  by 
throwing  the  cathode  wire  to  the  regulator 
terminal.  Some  of  these  tubes  also  have 
a  device  for  raising  the  vacuum.  By  a  current 
of  25  to  30  mills.,  a  metal  selenium  filament  is 
heated  which  in  its  incandescent  state  absorbs 
the  residual  gas.  The  advantages  claimed  for 
the  hydrogen  regulation  are  simplicity  and 
steadiness  of  tube  action,  for  with  the  mica, 
asbestos  or  chemical  regulators,  the  gases  en- 
tering the  tube  are  complex,  of  high  electrical 
resistance  and  poor  penetration.  Superiority 
over  the  oxygen  regulators  is  claimed  because 
of  the  affinity  which  oxygen  has  for  copper 
with  which  it  forms  oxides.  With  hydrogen, 
however,  the  electrical  and  penetrative  char- 
acteristics remain  uniform  indefinitely. 

Hard  tubes  can  be  made  soft  through  heat- 
ing, which  drives  particles  of  gas  from  the 
metal  parts  and  glass  wall  into  the  bulb.  This 
regeneration  is  only  transitory.  In  old  tubes, 
in  which  considerable  metal  has  been  de- 
posited, the  walls  are  very  unstable  and  hard, 
and  reduced  only  with  difficulty.  Tubes  made 
too  soft  may  be  made  harder  by  long  use  with 
a  weak  current,  the  residual  atoms  being 
driven  into  the  glass  of  the  bulb.  Reversing  the 
direction  of  the  discharge  and  allowing  it  to 
pass  from  cathode  to  accessory  anode  (dis- 
connecting the  target)  will  raise  the  vacuum. 

IV.  Variations  in  the  shape  and  size  of 
bitlbs     have     been     responsible     for     several 


types.  The  seven  inch  bulb  is  now  generally 
utilized.  For  gas  tubes  very  large  or  very 
small  bulbs  have  their  disadvantages.  e„The 
bulb  containing  the  targets  may  be  small,  but 
there  may  be  attached  to  it  a  large  accessory 
bulb.  The  purpose  of  such  a  construction  is  to 
permit  a  close  proximity  of  target. to  object — 
a  desirable  condition  in  therapy.  It  is  important 
that  the  tube  be  of  pure  crown  sodium- 
calcium-silicate  glass,  fluorescing  a  bright 
green,  ( lead  glass  fluoresces  blue ) .  and  that  the 
glass  wall  be  not  more  than  five  millimeters 
thick.  In  some  varieties  of  bulbs  the  glass  over 
the  central  part  of  the  active  hemisphere  is 
made  especially  thin,  in  order  to  diminish  the 
absorption  of  the  x-rays  in  the  glass  wall.  The 
entire  tube  may  be  of  lead  glass,  with  the 
exception  of  a  window  over  the  central  part 
of  the  active  hemisphere,  which  is  of  crown 
glass. 

Tubes  have  also  been  constructed  of  special 
glass,  made  of  salts  having  very  low  atomic 
weights,  lithium,  berylium  and  borax.  Such 
tubes  permit  one  hundred  per  cent  more  of 
the  soft  rays  to  emerge  from  the  tube,  raising 
the  total  output  to  about  eighty-five  per  cent. 

Those   are   called    Lmdemann    glass    tubes. 

Oval  tubes  have  been  constructed.  \'ery 
small,  unipolar  tubes  have  been  made  of 
various  shapes  for  insertion  into  the  various 
orifices  of  the  body. 

The  anodal  and  cathodal  glass  projections 
of  the  bulb  have  been  placed  in  various  posi- 
tions in  relationship  to  each  other  with  the 
purpose  of  increasing  the  distance  of  the  tube 
terminals  from  the  object  irradiated. 

The  bulb  of  a  small,  spherical  or  oval  tube 
may  be  surrounded  by  a  C3-lindrical  shield  of 
lead  glass. 

In  1912  the  author  introduced  an  x-ray  tube 
having  a  diameter  of  ten  centimeters,  into 
such  a  lead  glass  sleeve,  which  had  a  circular 
opening  for  the  free  emission  of  the  rays, 
thus  making  unnecessary  the  use  of  large, 
lead-glass  tube  shields.  This  form  of  shield 
has  of  late  been  utilized  for  shielding  the 
small  Coolidse  tube.  ^ 


VARIATIONS    IN    SHAPE   AND    SIZE 


67 


3'  32       3'3  • 

Fig.  82. — Types  of  X-Ray  Tubes. 

1.  The  first  tube  with  which  any  practical 
results  were  obtained.  In  this,  as  well  as  2,  3, 
and  4  which  show  modifications  in  form,  the 
cathode  was  flat  and  the  anode  was  a  large 
ring.  The  defect  in  these  early  tubes  was  the 
indistinctness  of  the  images  obtained.  It  soon 
necessitated  the  making  of  the  cathode  con- 
cave and  to  avoid  the  puncturing  of  the  glass 
at  the  point  of  convergence  of  the  cathode 
stream  a  piece  of  metal  was  placed  in  the  path 
of  the  stream.  This  piece  of  metal  was  placed 
opposite  the  cathode  and  called  the  anticathode 
target,  or  positive  electrode.  5,  6,  and  7,  con- 
structed on  the  same  plan  are  the  first  types  in 
which  focussed  cathode  rays  were  used.  In 
order  to  avoid  the  discharges  on  the  exterior 
of  the  tube,  between  two  electrodes,  the  tubes 
were  drawn  out  at  cathode  and  anode  end 
and  the  cathode  drawn  into  the  neck  of  the 
extension.  8  and  9  were  built  on  above  plan, 
and  a  ring  was  attached  to  the  target,  to  assist 
in  the  focusing  of  the  cathode  stream  and  to 
prevent  wandering  of  the  focal  spot.  10  and 
11. — An  accessory  anode  was  added.  12. — A 
collar  was  placed  about   the  target   with   the 


object  of  diminishing  the  production  of  diver- 
gent rays  and  the  consequent  secondary  ray 
production. 

The  addition  of  regenerating  devices  for 
lowering  the  vacuum  resulted  in  important 
changes  in  tube  construction.  The  first  tube 
with  such  a  device  for  lowering  the  vacuum 
is  shown  in  8.  This  had  a  small  accessory 
tube  containing  potash  which,  when  heated, 
gave  off  the  vapor  of  water.  In  order  to 
simplify  this,  the  regeneration  was  made  auto- 
matic by  means  of  a  shunt  from  the  negative 
end  of  the  tube  to  the  regulator,  the  sparking 
between  the  two  ends  heating  the  potash  until 
the  vacuum  reached  the  desired  point  — 9.  This 
was  followed  by  a  type  of  tube  in  which  the 
regeneration  took  place  by  heating  an  alumi- 
num spiral  wire — 13. 

18.  In  a  small  accessory  chamber  was 
placed  a  device  by  which  it  became  possible 
not  only  to  lower  the  vacuum  but  to  raise  it 
as  well.  A  mica  disc  when  heated  gave  off 
the  vapor  of  water  which  lowered  the  vacuum. 
A  fine  spiral  of  wire,  when  heated  from 
anodal  terminal  absorbed  the  gas  of  the  tube 
and  raised  the  vacuum.  The  use  of  heavy 
currents  demanded  heavy  targets  and  their 
cooling  by  means  of  water  (15),  modifications 
of  which  (20-33)  consisted  merely  of  the  es- 
tablishment of  intimate  contact  between  the 
water  and  the  target  itself.  The  position  of 
the  water  cooled  target  is  changed  to  permit 
the  placing  of  the  tube  horizontally. 

16.  Heavy  target  tube  for  large  currents. 
28,  30,  31.     Later  models  of  same. 

17.  Tube  with  two  cathodes  so  disposed  as 
to  give  dift'erent  hardness  to  the  ray  bundle. 

25.  Convex  cathode  and  double  anode. 

28,  30,  16.  Target  stem  and  target  envel- 
oped in  a  glass  sleeve,  with  reenforced  targets. 

29.  Unipolar  tube  for  use  with  high  fre- 
quency  currents. 

22-24.  Tubes  of  special  construction  for 
insertion  into  the  various  orifices  of  the  bodv. 


CHAPTER  \"II 

THE  HOT  CATHODE  OR  ELECTRON 

TUBES 

The  Coolidge  Tube 

The  production  of  x-rays  in  the  Coohdge 
tube  is  independent  of  the  state  of  the  vacuum, 
for  its  exhaustion  is  over  1,000  times  greater 


Fig.  83. — Coolidge  Tube. 

than  the  ordinary  tube.  The  cathode  is  so 
arranged  that  it  may  be  heated  electrically, 
either  by  battery  or  small  transformer.  An 
electrically  conducting  cylinder  connected  to  it 
serves  to  focus  the  cathode  rays  on  the  target. 
The  filament  ( A )  Fig.  85.  which  forms  the 
cathode,  consists  of  a  flat,  closely  wound 
spiral  of  tungsten  wire.  The  spiral  tung- 
sten wire  is  mounted  concentrically  within 
a  cylindrical  tube  of  molybdenum  (  B  )  Fig.  85, 
which    projects    about    0.5    mm.    beyond    the 


plane   of  the   filament.     The   cylindrica^  tube 
serves  to  focus  the  cathode  stream. 

The  anticathode  or  target,  Fig.  84,  which 
also  serves  as  anode  consists  of  a  single  piece 
of  wrought  tungsten  (C)  attached  to  a  molyb- 
denum rod  (D)  and  supported  by  a  split 
iron  tube  (E).     Because  of  the  high  vacuum 


/ 


Fig.  84. — Anode  of  Coolidge  Tube. 

the  tube  offers  infinite  resistance  to  the  pas- 
sage of  a  current  of  any  potential.  The 
vacuum  may,  however,  be  rendered  conductive 
by  the  heating  of  the  filament  (A)  to  incan- 
descence. 

The  low  tension  current  for  heating  the  fila- 
ment may  be  obtained  from  a  storage  battery 
or  a  step-down  transformer,  wherever  alter- 
nating current  is  available.  This  transformer 
must  be  insulated  for  100,000  volts  and  be 
capable  of  dehvering  6  am.peres  at  12  volts.  In 
case  it  is  necessary  to  obtain  the  alternating 
current  from  the  same  source  of  supply  as  that 
of  the  x-ray  transformer,  or  only  direct  current 
is  available,  the  storage  battery  is  preferable. 
But  where  there  are  two  separate  sources  of 


Fig.  85. — Cathode  of  Coolidge  Tube. 

alternating  current  supply,  then  the  filament 
transformer  is  to  be  recommended.  A  small 
rotary  convertor  may  be  utilized  where  only 
direct  current  is  available,  to  supply  alternating- 
current  to  the  filament. 

If  a  battery  is  used  it  should  be  a  5-  or  6-cell 
(10-  or  12-volt),  40  ampere-hour  battery  and 
arrangements  should  be  made  so  that  the  bat- 


[68] 


COOLIDGE  TUBE  CIRCUIT 


69 


tery  can  be  connected  during  the  night  to  a 
charging  circuit.  In  order  to  allow  the  bat- 
tery to  reach  a  stable  condition  and  eliminate 
fluctuations  in  the  filament  current,  the  fila- 
ment circuit  should  be  closed  a  few  minutes 
before  the  tube  is  used.  (A  fully  charged  bat- 
tery shows  2.5  volts  per  cell,  dropping  rapidly 
to  a  stable  point  of  2  volts.)  It  is  advisable  to 
charge  the  battery  at  frequent  intervals, 
owing  to  its  instability  of  voltage. 

If  long  battery  leads  become  necessary,  they 
add  resistance  to  the  filament  circuit,  so  that 
either  additional  cells  must  be  added  or  heavier 
wire  leads  used. 

It  must  ahvays  be  borne  in  mind  that  the 


Fig.  86. — Step-down  transformer  and  interrupter  for 
use  with  Coolidge  filament.   (Jordan.) 

entire  battery  circuit  is  brought  to  the  full 
potential  of  the  tube  and  that  it,  therefore,  has 
to  be  as  thoroughly  insulated  from  the  patient 
and  the  ground  as  the  tube  itself. 

Jordan  has  suggested  the  use  of  an  inter- 
rupter in  conjunction  with  a  small  step-down 
transformer.  A  rheostat  in  the  primary  circuit 
provides  the  regulation.  A  motor-magnetic 
interrupter   is   used. 

A  full  Coolidge  circuit  is  shown  in  diagram, 
Figs.  87,  89,  in  which  the  double  reel  goes  to 
the  cathode  end  of  the  tube,  one  lead  to  the 
amperemeter  the  other  to  the  secondary  of  the 
step-down  transformer.  The  rheostat  for  con- 
trolling the  current  in  the  filament  circuit  is  in 
the  primary.  A  small  rotary  converter  is  used 
where  only  d.  c.  is  available.  The  technique  for 
the  Coolidge  tube  work  demands  the  use  of 
an  ammeter  in  the  filament  circuit.  The  meter 
should   have    a    5-ampere    scale,    divided   into 


l/50th  ampere  divisions,  large  enough  to  be 
easily  and  accurately  read.  A  scale  reading 
from  3  to  5  is  sufficient  since  these  are  the 
limits  for  practical  radiology.  The  meter 
should  be  located  as  close  to  the  operator  as 


^;l!l!l'lt- 

B  A 

Fig.  87. — Coolidge  tube  circuit  B  is  the  storage  bat- 
tery, A  is  the  ammeter,  R  is  the  rheostat  for 
regulation  of  the  battery  current.  The  double 
wires  go  to  the  cathode  end  of  the  tube.  M 
is  the  milliamperemeter. 

possible  and  in  such  a  way  that  it  can  be  easily 
read  from  the  operating  position. 

If  the  polarity  of  the  machine  is  wrong,  it 


Fig.  88. — Storage  battery  arrangement  for  Coolidge 
tube  with  attachment  for  charging.  When  the 
extension  to  the  right  is  placed  vertically  the 
battery  charges.     (W'aite  and  Bartlett). 


will  be  shown  by  the  fact  that  the  milliam- 
meter  will  register  no  current,  regardless  of 
how  high  the  filament  temperature  may  be. 

Before  the  tube  can  be  energized  it  is  neces- 
sary to  heat  the  filament. 


70 


ENERGIZATION  OF  COOLIDGE  TUBE 


No  discharge  current  through  the  tube  can 
take  place  unless  the  filament  is  heated, 
and  the  amount  of  discharge  current  which 
may  be  passed  into  the  tube  is  determined  pri- 
marily by  the  degree  of  heating  of  the  fila- 
ment. 

If  the  temperature  of  the  filament  is  low, 
only  a  small  number  of  electrons  escape  from 
it  and,  consequently,  only  a  small  discharge 
current  can  be  sent  through  the  tube.  The 
maximum  current  for  each  particular  filament 
temperature  is  called  the  saturation  current 
which  means  that  all  the  electrons  are  being 
utilized  as  fast  as  they  are  produced.  Increas- 
ing the  impressed  voltage  above  that  needed 


Fig.   89. — Connections    for   Coolidge   filament   trans- 
former and  control. 

for  this  current  value  causes  no  further  in- 
crease in  current.  It  simply  increases  the 
velocity  of  the  cathode  rays  and  hence  the 
penetrating  power  of  the  x-rays. 

The  penetrating  power  of  the  x-rays  gen- 
erated, however,  is  dependent  on  the  voltage 
of  the  energizing  current.  The  size  of  the 
focal  spot  determines  the  amount  of  energy 
input,  which  may  be  used  with  a  particular 
tube  for  the  efficient  production  of  x-rays 
without  damage  of  the  tube.  A  fine  focal 
point  would  be  below  2  mm.,  a  medium  point 
would  be  from  2  to  4  mm.,  and  a  broad  one 
over  4mm. 

The  finer  the  focal  spot  the  less  the  capacity 
of  the  tube.  The  safety  limits  are  for  fine 
focus  25  milliamperes,  medium  50,  broad 
80  milliamperes,  with  the  equivalent  voltage 
represented  by  a  6"   parallel   spark  back-up. 


For  fluoroscopy  and  where  sharp  definition  in 
radiographic  work  is  reqitired  the  fine  focus 
is  used;  in  therap}'  the  broad  focus.  In  "Spite 
of  this  the  tube  is  capable  of  considerable 
usage,  under  conditions  of  continuous  opera- 
tion without  change  of  characteristics.  • 


Type  "A' 


Fine 


Medium 


Broad 


Fine    Focus — Capacity    25    ma. 

at  a  6"  equivalent  spark  gap. 

Watts    Capacity   of    target 

.025  X  70000  =  1750  watts 

or  I.7S  K.  V.  A. 

Equivalents  ; — 

29.2  ma.  at  5"  Spark 
35-       "     "    4"       " 
43.7     "     "    3"       " 


Medium     Focus — Capacity     SO 
ma.  at  a  6"  equivalent  spark 

gap- 
Capacity   of   target.    .05   x 
70000  :=  3500     watts     or 
3.5  K.  V.  A. 
Equivalents  : — 

58.4  ma.  at  5"  bk  up 
70.  "  "  4"  "  " 
87.4     "     "    3"    "     " 


Broad  Focus — Capacitj'  80  ma. 

at   6"    equivalent   spark   gap. 

Wattage   capacity.     .080   x 

70000  =  i;6oo  watts  or  5.6 

K.  V.  a'. 

Equivalents  : — 

93.3  at  5"   Back  up 
100.      "     4" 
140.      "     3"       " 


Fig.  90.- 


-Focal  points  of  various  types  of  Coolidge 
tubes. 


The  tube  may  be  safely  run  with  the  target 
at  white  heat.  If  excessively  high  energy  in- 
puts are  employed,  the  tungsten  at  the  focal 
spot  melts  and  volatilizes.  This  results  in  a 
sudden  lowering  of  the  tube  resistance  and  in 
blackening  of  the  bulb.  The  instability  in  re- 
sistance   disappears    instantly    upon    lowering 


VARIETIES  OF  COOLIDGE  TUBES 


71 


the  energy  input,  and  no  harm  has  been  done 
to  the  tube — that  is,  unless  it  is  to  be  used  for 
the  production  of  the  most  penetrating  rays 
which  it  is  capable  of  emitting.  In  this  case, 
a  heavy  metal  deposit  on  the  bulb  is  undesir- 
able, as  it  interferes  with  smooth  running  at 
such  high  voltages. 

There  is  no  fluorescence  of  the  glass  of  the 
tulx-.  This  is  due  to  the  absence  of  positive 
ions  and  the  accumulation  of  a  negative 
charge  on  the  glass,  which  repelling  the  elec- 
trons prevents  the  glass  from  being  a  target. 

The  tube  should  not  be  run  with  a  voltage 
higher  than  that  corresponding  to  a  10-in. 
spark  gap  between  points    (that  is,  it  should 


1.  It  permits  a  great  reduction  in  tlie  size 
and  weight  of  the  tube  holder  for  the  same 
amount  of  x-rays  produced. 

2.  It  permits  a  closer  approach  of  the  dia- 
phragms to  the  focal  spot  and  gives  better 
definition. 

3.  It  permits  a  closer  approach  of  the  focal 
spot  to  the  part,  this  being  an  advantage  in 
therapeutic  application. 

4.  It  decreases  the  danger  of  tube  breakage 
in  handling. 

The  focal  spot  of  the  target  of  this  tube  is 
extremely  fine,  below  2  mm,  and  excellent  de- 
tail may  be  obtained  in  the  radiograph. 

Because  of  the  verv  fine  focus  the  amount 


Fig.  gi. — Fine  focus  small  bulbed  Coolidge  tube  with  radiator.  For  portable  work  a  sleeve  of 
lead  glass  is  slipped  over  the  tube.  The  target  is  a  tungsten  button  set  in  a  solid  block  of 
copper  welded  to  a  copper  stem.  The  radiator  is  so  efficient  in  carrying  off  the  heat  as  to 
make  this  tube  self-rectifying  and  capable  of  use  with  a  transformer  without  a  rectifying 
device. 


not  be  made  to  back  up  more  than  a  10-in. 
parallel  gap). 

For  long  continued  running  in  an  enclosed 
space  and  with  heavy  energy  inputs,  it  will 
be  necessary  to  provide  some  means  of  cooling 
the  glass,  as  by  a  small  fan  or  blower. 

In  energizing  a  tube  by  an  induction  coil,  a 
valve  tube  should  be  used  where  heavy  energy 
inputs  are  to  be  employed.  So  long,  Jiozvcvcr, 
as  flic  temperature  of  the  focal  spot  docs  not 
approximate  that  of  the  cathode,  the  tube  zvill 
satisfactorily  rectify  its  ozi'ti  current. 

Varieties  of  Coolidge  Tubes 

The  ordinary  form  of  Coolidge  tube  is  a 
bulb  7"  in  diameter,  having  the  characteristics 
above  described.  Another  form.  Type  "A," 
has  lately  been  produced,  the  tube  being  but 
334"  in  diameter  and  18"  in  length.  The 
spiral  is  set  in  the  center  of  a  concave  cathode. 

The  chief  advantages  of  the  smaller  bulb 
are  as  follows : 


of  energy  W'hich  can  safely  be  used  is  small, 
as  indicated  in  the  table  : 

M.  A. 


Spark 


25 
17 
12 
10 


2  in. 

3  in. 

4  in. 

5  in. 

6  in.  8 

When  radiographic  work  is  being  done, 
using  the  maximum  amounts  of  energy  which 
this  tube  will  stand,  an  exposure  of  over 
twenty-seconds  is  not  recommended  and  the 
exposure  should  be  begun  with  the  tempera- 
ture of  the  target  below  a  visible  red. 

If  the  maximum  amount  of  energy  is  ex- 
ceeded, the  metal  at  the  focal  spot  will  melt 
and  volatilize  and  condense  on  the  bulb  as  a 
heavy  metallic  deposit  which  renders  the  tube 
liable  to  puncture.  This  melting  may  also 
cause  gas  to  be  liberated  in  the  bulb  which 
causes  the  tube  to  operate  unsatisfactorily. 

The  small  amounts  of  energy  that  this  tube 


72 


LILLIENFELD  TUBE 


is  capable  of  carrying  is  partially  compensated 
for  radiographic  work  by  the  extremely  fine 
focus  which  permits  the  focal  distance  to  be 
greatly  decreased  without  sacrificing  any  of 
the  detail,  but  with  considerable  shortening  of 
the  exposure. 

This  tube  is  particularly  valuable  for  fluoro- 
scopic work,  and  in  dental  radiography,  as  it 
permits  a  closer  approach  to  the  part  being 
rayed  and  gives  excellent  detail. 


by  this  means  the  target  can  be  kept  at  a  tem- 
perature less  than  the  cathode  a  rectifier  of 


Fig.  92.Lillienfeld  tube  circuit  with  three 
transformers. 


This  type  of  tube  is  not  recommended  for 
therapeutic  work. 

A  water  cooled  target  has  been  used  in  the 
Coolidge  tube,  the  water  being  brought  close 


Fig.  93. — Lillienfeld  tube  circuit.  One  of  the  trans- 
formers has  been  eliminated,  the  voltage  neces- 
sary for  (K)  is  obtained  from  (T)  by  means  of 
a    variable    high-tension    resistance (R). 

to  the  face  of  the  target.  Such  a  tube  has 
been  energized  continuously  with  100  milli- 
amperes  and  70,000  volts  for  many  hours.     If 


Fig.  94. — The  Lillienfeld  tube. 

the  secondary  discharge  becomes  unnecessary. 

To   prevent   the   production   of    rays    from 

other  sources  than  the  focal  spot  a  cylindrical 


METAL  TUBE 


73 


cap  of  molybdenum  has  been  attacbed  to  the 
front  of  the  target  of  the  Coohdge  tube.  Ca- 
thode rays  enter  the  hood  through  a  hole  in 
the  front,  and  the  x-rays  emerge  through  a 
hole  in  the  side.  Several  advantages  have  been 
claimed  for  this  tube,  the  important  one  being 
that  it  reduces  the  radiation  from  the  surface 
of  the  target,  exclusive  of  the  focal  spot,  to 
about  1/6. 

Another  form  of  Coolidge  tube  has  a  target 
of  tungsten  set  in  a  large  copper  block  which 
is  part  of  a  copper  rod  extending  out  of  the 
tube  and  having  attached  to  it  a  radiator  in  the 
form  of  discs  which  serve  to  radiate  or  dissi- 
pate the  heat  into  the  air.  (Fig.  91.)  This 
tube  is  used  with  the  portable  and  bedside 
units  of  the  United  States  army  which  have 
no  commutating  devices.  For  with  10  milli- 
amperes  at  a  5-inch  spark  gap,  the  target  heat 
does  not  approximate  that  of  the  filament.  A 
similar  30  milliampere  tube  has  been  devised. 

The  Lillienfeld  Tube 

Another  form  of  hot  cathode  tube  was  de- 
scribed by  Lillienfeld  in  1910  and  1914.  The 
tube  is  of  oval  shape,  consists  of  two  parts 
(Fig.  94),  an  anodal  and  a  cathodal,  con- 
nected by  a  neck,  which  contains  a  hollow 
cathode.  The  cathodal  end  contains  a  filament, 
and  is  the  electron  generating  portion  of  the 
tube,  the  anodal  end  contains  the  target  and 
is  the  x-ray  generating  portion.  The  tube 
is  water-cooled.     Its  mechanism  is  as  follows : 

The  incandescent  filament  G  (Fig.  92)  is 
kept  at  a  high  and  constant  temperature  by 
means  of  a  stepdown  transformer  H.  A 
secondary  current  of  5,000  volts  and  several 
milliamperes  generated  by  a  high  tension 
transformer  Z  is  connected  to  the  incandes- 
cent filament  G  and  the  perforated  cathode  IC, 
creating  an  electrostatic  field,  which  drives 
the  electrons  generated  by  the  filament 
through  the  perforated  cathode  K.  The 
regular  high  tension  transformer  or  coil 
T  is  connected  to  the  cathode  and  target, 
and  this,  when  energized,  drives  the  cathode 
stream  against  the  target  and  generates  x-rays. 
The   production   of   rays   is   regulated   by   the 


5,000  volt  transformer  discharge.  The  greater 
this  is,  the  larger  the  quantity  of  cathode  rays 
forced  through  the  cathode,  the  lower  the 
secondary  voltage  and  the  softer  the  x-rays 
produced.  Diminishing  the  electrostatic  dis- 
charge sends  fewer  electrons  through  and 
causes  an  increase  in  the  x-ray  tube  potential 
and  an  increase  of  the  penetrability  of  the 
x-rays. 

Three  currents  are  therefore  necessary  for 
the  use  of  the  Lillienfeld  tube: 

L  A  low  voltage  (about  14  volts,  4  am- 
peres), for  heating  the  incandescent  cathode. 

2.  A  high-tension  current  of  about  5,000 
volts. 

3.  The  regular  high  tension  current  from 
transformer  or  coil. 

The  current  of  5,000  volts  and  the  high  ten- 
sion discharge  from  the  transformer  must  be 
in  synchronism. 

Practically  the  energizing  system  may  be 
simplified  by  the  elimination  of  the  5,000  volt 
transformer  so  that  the  voltage  necessary  for 
the  electrostatic  field  is  tapped  from  the  large 
transformer  by  the  insertion  of  a  high  tension 
resistance.  (Fig.  93).  The  high  tension  x-i-ay 
transformer  or  coil  is  connected  directly  with 
the  anti-cathode  of  the  x-ray  tube  and  the  in- 
candescent cathode  G.  The  incandescent 
cathode  G  is  heated  by  the  low  tension  cur- 
rent as  above.  By  varying  the  resistance,  the 
electrostatic  discharge  is  controlled  and  the 
degree  of  penetration  of  the  rays  varied. 

Metal  Tube 

Such  a  tube  has  been  described  by  Zehnder. 
The  body  of  the  tube  is  of  copper.    (Fig  95). 

As  described  by  Coolidge,  the  cathode  /, 
projects  into  a  and  is  supported  and  insc'.aced 


Fig.  95. — :Metal  tube, 
from  it  by  the  glass  tube  c.  Z?  is  a  flaring 
piece  of  thin  walled  platinum  tubing  which 
is  silver-soldered  at  the  small  end  to  the 
copper  tube  and  sealed  at  the  large 
end  to  r.  The  hot  cathode  /.  is  supported  by 
means  of  the  copper  tube  c.  which  at  the  outer 


74  METAL  TUBE 

end  is  enlarged  and  fitted  tiglitly  on  to  the  a  considerable   fraction  of  the  roentgen  rays 

glass  tube  d.     Of  the  two  copper  wires  carry-  produced  on  the  side  next  to  the  cathode  pass 

ing  current  in  to  the  filament,  the  one  marked  through  it  and  are  available   for  use  oj)  the 

h  is  metallically  connected  to  c,  while  the  other  other  side.     In  operation,  the  metal  body  of 

is  insulated.     (/  is  a  window  of  thin  platinum  the  tube  is  connected  to  the  positive  terminal 

which  also  serves  as  target.     It  is  so  thin  that  of  the  generator. 


CHAPTER  MIT 
THE  CATHODE  DISCHARGE 

For  a  clear  understanding  of  the  methods 
of  production,  the  nature  and  characteristics  of 
the  x-rays,  a  few  words  must  be  said  of  the 
cathode   rays. 

The  cathode  discharge  consists  of  a  stream 
of  negatively  charged  electrons  having  the 
mass  of  1/1800  of  a  hydrogen  atom.  The 
velocity  of  the  electrons  in  the  stream  is  about 
one  one-thirtieth  to  one-third  of  that  of  light, 
6.210  to  62,100  miles  per  second,  but  varies 
with  the  e.  m.  f .  applied  to  the  tube. 

In  a  gas  tube  the  electrons  are  due  to  dis- 
ruption of  atoms  by  a  highly  charged  electric 
field.  In  a  Coolidge  tube  they  are  obtained 
from  a  tungsten  wire  heated  to  incandescence. 

The  charge  which  the  electrons  bear  is  small 
but  constant.  In  radium  the  release  of  elec- 
trons (B-rays)  results  in  the  production  of 
gamma  rays,  but  in  the  vacuum  tube  it  is  by 
the  sudden  stopping  of  electrons  moving  at  a 
high  speed  in  an  electric  field  that  x-rays  are 
obtained. 

If  no  extraneous  influences  are  at  work  the 
cathode  electrons  leave  the  cathode  perpen- 
dicularly to  its  surface.  The  forces  which 
are  capable  of  influencing  the  cathode  stream 
are  either  magnetic  or  electrostatic.  The  greater 
the  strength  of  the  magnetic  field,  and  the 
less  the  rapidity  of  movement  of  the  cathode 
stream,  the  greater  deviation  produced.  The 
speed  of  the  cathode  stream,  too,  depends 
considerably  upon  the  impressed  voltage  and 
the  vacuum  of  the  tube.  With  the  same 
potential  ditTerence  between  the  terminals  of 
the  tube,  the  higher  the  vacmun,  the  more 
rapidly  do  the  electrons  move.  This  refers 
to  a  gas  tube.  In  an  electron  or  Coolidge  tube, 
the  speed  is  determined  directly  by  the  poten- 

NoTE. — It  is  now  possible  to  produce  cathode  rays 
having  a  velocity  comparable  with  that  of  the  most 
rapidly  moving  beta  rays  from  the  radio-active  sub- 
stances, and  at  the  same  time,  to  produce  x-rays 
■comparable  in  penetrating  power  with  the  most 
penetrating  gamma  rays. 


tial  difference  between  the  terminals.  The  ca- 
thode stream  consists  of  both  slowly  and  rapid- 
ly moving  electrons.  The  application  of  a  mag- 
net will  therefore  result  in  a  separation  of 
the  cathode  stream  into  two  parts,  the  slowly 
moving  electrons  will  be  deviated  and  the 
rapidly  moving  ones  will  not  be.  Visualized 
on  a  fluorescent  screen  this  eft'ect  is  shown 
by  a  series  of  bright  lines,  the  "  magnetic 
spectrum  "  of  the  cathode  stream. 

Deviation  of  the  cathode  stream  will  take 
place  if  an  electrostatically  charged  conductor 
is  placed  in  its  proximity. 

The  deviation  of  the  stream  occurs  normally 
by  reason  of  the  electrostatic  charge  residing 
on  the  glass  wall  of  the  tube,  when  the  tube 
is  energized.  It  is  more  intense  in  tubes  of 
low  vacuum. 

The  magnetic  deviation  of  the  cathode 
stream  has  a  certain  practical  bearing.  The 
transformer  used  for  the  energizing  of  the 
tube,  because  of  its  iron  core,  becomes  mag- 
netic. If  the  tube  is  placed  too  near  the  appa- 
ratus, then  the  cathode  beam  or  bundle  may  be 
strongly  deviated  away  from  the  focal  spot 
on  the  target.  To  avoid  this,  low  vacuum 
tubes  should  not  be  operated  less  than  five  feet 
distant  from  the  transformer.  If  this  condi- 
tion is  unattainable,  it  is  important  to  main- 
tain the  tube  ends  an  equal  distance  from  the 
apparatus.  It  is  because  of  the  electro-static 
effects  that  the  relation  of  the  cathode  cup 
to  its  glass  wall  is  important,  for  the  deter- 
mination of  the  quality  of  ray  and  steadiness 
of  the  tube  activity. 

The  magnetic  deviation  of  the  cathode 
rays  is  utilized  to  concentrate  them.  By  in- 
troducing in  the  cathode  a  wire  spiral  and 
heating  it  electrically,  Furstenau  was  able  to 
concentrate  the  cathode  rays  into  a  fine  stream 
and  bring  it  thus  to  the  target. 

Such    a    glowing    wire,    introduced    into    a 
vacuum  emits  electrons,  the  quantity  of  emis- 
sion depending  upon  the  temperature  of  the 
wire.     The   negative   ions   emitted   are   about 
1751 


76 


PROPERTIES  OF  CATHODE  RAYS 


1/1800  of  the  size  of  a  hydrogen  atom,  while 
the  positive  ions  have  atomic  or  molecular  di- 
mensions. A  vacuum  which  offers  almost  in- 
finite resistance  to  the  passage  of  electricity 
will,  when  the  glowing  wire  is  introduced, 
acquire  electrical  conductivity. 

This  principle  is  utilized  in  the  construction 
of  the  cathode  of  the  tubes  already  described. 

The  characteristics  of  cathode  rays  are  as 
follows : 

1.  They  have  the  power  of  penetrating  sub- 
stances opaque  to  light  but  to  a  degree  consid- 
erably less  than  the  x-rays  they  are  capable  of 
generating.  A  sheet  of  aluminum  of  0.0064 
mm.  thickness  or  platinum  of  0.00074  mm. 
thickness  is  sufficient  to  absorb  99%  of  a 
cathode  ray  bundle.  If  transformed  into  x- 
rays,  four  hundred  times  that  thickness  of 
aluminum  and  thirty-two  times  that  thickness 
of  platinum  will  be  required  to  absorb  the 
same  amount  of  energy. 

Ordinary  glass  has  about  the  same  absorp- 
tive quality  as  aluminum  in  this  regard  and 
the  amount  of  cathode  rays  penetrating  the 
glass  wall  of  the  tube  is  therefore  small. 

2.  Cathode  rays  excite  fluorescence.*  The 
fluorescence  which  extends  over  half  of  the 
glass  wall  is  not  caused  by  the  original  or  pri- 
mary cathode  ray  bundle  of  the  tube,  because 
this  is  directed  to  the  anticathode,  but  is  due  to 
the  action  of  the  so-called  secondary  cathode 
rays  on  the  positive  ions  on  the  inner  surface 
of  the  glass  bulb  and  to  this  cause  is  also  due 
the  heating  the  glass  wall  of  the  tube. 

The  fluorescence  which  the  secondary  cath- 
ode rays  cause  in  the  glass  wall  of  the  tube  is 

*  Note. — Fluorescence  is  a  phenomenon  in  which 
radiant  energy  of  one  wave  length  is  absorbed  by 
a  material  and  emitted  as  radiant  energy  of  a  longer 
wave  length. 


a  rough  index  of  the  quality  and  quantity  of 
the  x-rays,  as  will  be  pointed  out  later.  That 
is  to  say,  a  tube  of  low  vacuum  will  flrferesce 
a  more  brilliant  and  darker  green  than  one 
of  high  vacuum. 

3.  Heat  is  generated  on  the  anticathode  by 
the  impact  of  the  cathode  rays.  It  is  one 
hundred  and  forty  thousand  times  as  great  as 
that  produced  by  the  most  intensive  sunlight. 
Since  the  sharp  focusing  of  the  stream 
is  essential,  in  order  to  obtain  sharp  radio- 
graphs, the  metallic  anticathode  must  be  of 
such  consistency  that  disintegration  of  the  tar- 
get with  emission  of  gas  and  a  change  in  the 
vacuum  will  not  occur.* 

4.  The  cathode  rays  disintegrate  the  ca- 
thode. The  disintegration  varies  with  differ- 
ent substances.  Aluminum  is  scarcely  af- 
fected ;  platinum,  however,  considerably  so. 

5.  The  cathode  rays  have  ionizing  power, 
rendering  a  gas  electrically  conductive.  It  is 
by  virtue  of  this  effect  on  the  residual  gas  in 
an  x-ray  tube  that  the  cathode  discharge  be- 
comes visible  as  a  luminous  streak. 

6.  The  cathode  stream  generates  x-rays  at 
a  point  of  impact  of  its  electrons  against  a 
target — solid,  liquid  or  gaseous. 

"The  higher  the  electron  speed  and  the  more 
effective  the  target  material  in  quickly  stop- 
ping them  the  more  penetrating  the  result- 
ing radiation.  The  nature  and  amount  of 
the  y  or  roentgen  radiation  due  to  any  single 
electron  depends  only  on  the  changes  in  its 
Ppeed.  So  that  the  amount  and  the  quality  of 
the  beam  (group  of  rays)  depend  on  the  aggre- 
gate action  due  to  the  group  of  electrons  con- 
sidered."    (Shearer). 

*  Note. — The  slower  the  speed  of  the  cathode  rays, 
the  more  of  its  energy  is  changed  to  heat. 


CHAPTER  -IX  ■ 
THE  X-RAY  AND  ITS   PROPERTIES 

The  researches  of  Roentgen  showed  that 
the  rays  in  some  respects  resembled  hght. 
They  moved  in  straight  Hnes  and  cast  sharp 
shadows,  traversed  space  without  change  in 
form  and  content,  acted  on  photo-plates,  ex- 
cited phosphorescence,  and  ionized  gases. 
Thev  could  not,  however,  bj-  any  means  then 
known,  be  reflected,  polarized  or  refracted. 

Since  the  wave  lengths  of  the  x-rays  were 
many  thousand  times  smaller  than  that  of 
sodium  light  and  since  the  later  is  refracted 
twenty-four  degrees  by  a  grating  which  al- 
ready has  seven  thousand  lines  to  the  centi- 
meter, it  was  obviously  impossible  to  construct 
a  grating  for  x-rays,  for  it  would  begin  to  ap- 
proach infinitesimal  divisions. 

But  in  1912  Laue  predicted  that  if  the  x- 
rays  were  passed  through  a  crystal,  the  inter- 
ference effects  would  be  produced  just  as  they 
are  when  ordinary  light  falls  on  a  Rowland 
grating ;  in  other  words,  the  crystal  planes 
would  serve  as  a  diffraction  grating.  The  ex- 
periment was  tried  by  Friedrich  and  Knipping 
and  the  prediction  proved  true.  The  problem, 
however,  was  not  so  simple,  because  the  atoms 
of  the  crystal  arrangement  extend  through 
three  planes. 

Bragg  showed  that  the  regular  reflection  of 
x-rays  can  be  made  to  take  place  from  the 
cleavage  surface  of  crystals. 

There  is  thus  obtained  a  radiographic  pat- 
tern of  the  refracted  beams,  arranged  around 
the  primary  beam  and  the  pattern  is  always 
the  same  for  the  same  crystal.  By  using  the 
same  crystal  piece  the  wave  lengths  of  differ- 
ent monochromatic  rays  may  be  compared 
and  by  using  a  ray  of  the  same  wave  length 
the  spacing  of  the  atomic  planes  of  various 
crystals  may  be  estimated. 

The  above  experiment  made  it  possible  to 
measure  the  wave  lengths  of  x-rays  and  show 
them  to  be  transverse  vibration,  traveling  with 


a  velocity  of  light  and  with  a  wave  length  of 
about  1/10000  of  that  of  light. 

jMoseley  and  Darwin  have  found  that  each 
element  when  used  as  a  target  in  an  x-ray  tube 
emits  x-rays  of  different  wave  lengths,  and  if 
the  emitted  ray  is  analyzed  by  means  of  a 
crystal,  an  x-ray  spectrum  may  by  photo- 
graphic means  be  obtained  showing  charac- 
teristic lines  for  every  metal.  It  was  found 
that  the  wave  length  increases  as  the  atomic 
weight  diminishes.  Each  element  when  placed 
in  the  path  of  x-rays  of  sufficiently  high 
penetration,  gives  off  secondary  rays  charac- 
teristic of  the  element.  The  researches  on 
crystal  reflection  have  demonstrated  that  the 
resemblance  of  x-rays  to  light  is  a  very  close 
one.  In  fact  x-rays,  light  and  the  gamma  rays 
of  radium  are  alike  in  origin  and  nature  and 
differ  only  in  wave  length. 

There  are  six  characteristics  of  the  x-rays 
which  deserve  special  consideration : 

1.  Their  effect  on  photographic  plates. 

2.  Their  ability  to  cause  fluorescence. 

3.  Their  penetration  of   substances  opaque 

to  light. 

4.  Their  ability  to  affect  the  living  cell. 

5.  Their    power    of    causing    chemical    re- 

actions. 

6.  Their  ionizing  power. 

Roentgenography  is  based  on  the  first  char- 
acteristic and  roentgenoscopy  or  the  screen 
examination  on  the  second.  The  above 
effects  do  not  parallel  each  other.  A  ray  of 
great  penetrability  ma}"  have  little  photo- 
graphic effect  and  cause  no  marked  fluores- 
cence. Rays  causing  the  same  degree  of 
fluorescence  may  have  diff'erent  photographic 
eff'ects. 

1.  The  reaction  of  x-rays  to  bromide 
of  silver  plate  is  similar  to  that  of  light 
in  quality  "but  not  in  quantity.  The  formation 
of  the  latent  image  both  by  light  and  x-rays 
is  due  to  the  emission  of  an  electron  by  a 
molecule  of  silver  salt.  This  suffices  to  make 
the  entire  crystal  of  the  salt  developable.     A 


[77i 


78 


PROPERTIES  OF  X-RAYS 


plate  may  be  very  sensitive  to  light  and  yet 
relatively  slow  to  react  to  x-ray.  Light  acts 
on  the  surface  and  the  emulsion  may  be  thin 
but  for  x-ra_vs  one  or  more  thick  layers  of 
emulsion  over  each  other  is  necessary.  The 
reaction  is  not  proportionate  to  the  direct 
absorption  of  the  x-rays  by  the  emulsion.  The 
most  intense  effects  are  obtained  with  rays 
emanating  from  a  low  tube,  for  these  are  able 
to  excite  the  characteristic  secondary  radia- 
tions of  the  elements  in  the  emulsion. 

2.  Fluorescence.  Salts  of  barium  platino- 
cyanide,  molybdenum  and  calcium  tungstate, 
silicate  and  sulphide  of  zinc,  calcium  molyb- 
date,  salicylate  of  ammonium  become  luminous 
when  exposed  to  x-rays.  The  substances 
are  said  to  be  fluorescent,  because  with  the 
cessation  of  the  exciting  rays  the  glow  ceases 
in  contradistinction  to  such  substances  as  zinc 
blende  in  which  the  glow  is  maintained  for  a 
long  time  after  the  cessation  of  the  exciting 
radiation.  This  latter  phenomenon  is  phos- 
phorescence. Platino-barium  cyanide  fluor- 
esces green  and  calcium  tungstate  blue.  The 
zinc  blende,  which  consists  of  artificially 
crystallized  sulphide  of  zinc,  fluoresces  blue 
during  exposure  and  phosphoresces  green 
after  it.  The  zinc  oxide  fluoresces  white  and 
the  silicate  yellowish  green.  This  property 
of  the  rays  is  utilized  in  making  directly  mani- 
fest to  the  retina  the  penetrability  of  the  ray. 

Because  of  the  blue  fluorescence  of  the  tung- 
state and  its  greater  photo-chemical  effect,  *  it 
is  used  in  the  construction  of  intensifying 
screens,  while  the  platino-barium  cyanide  is 
used  for  fluoroscopic  screens.  The  fluor- 
escence of  the  screen  under  the  rays  is  utilized 
to  intensify  the  action  of  the  ray  itself  on 
the  photographic  plate.  The  screen  consists 
of  the  pulverized  salt  suspended  and  coated 
on  cardboard  and  covered  with  enamel  for 
protection  against  dust  and  moisture. 

3.  X-rays  penetrate  substances  inversely 
in  proportion  to  their  density,  atomic  weight 
and  thickness. 

The  x-rays  themselves  vary  in  their  pene- 

*  Edison  investigated  i8oo  substances  before 
adopting  the  tungstate  of  calcium   for  this  purpose. 


trative  power  depending  on  the  degree  of 
vacuum  of  the  tube  and  other  factors  to  be 
considered.  They  are  described  as  liard,  when 
they  have  high  penetrative  power,  medium, 
when  their  penetration  is  less  and  soft  when 
it  is  feeble. 

The  absorption  of  the  roentgen  rays  by  a 
substance  depends  upon  its  thickness,  its 
atomic  weight  and  its  density,  but  is  entirely 
independent  of  the  manner  in  which  the  atoms 
are  grouped  and  of  whether  the  body  is  in 
liquid,  solid  or  vaporous  state. 

Carbon  is  equally  penetrable  to  the  roentgen 
rays,  whether  it  is  in  the  form  of  diamond  or 
graphite,  if  the  layers  are  of  the  same  density. 
Carbon  has  about  1/15  the  absorbing  ability 
of  aluminum,  1/29  of  sulphur  and  1/74  of 
calcium.  Though  the  first  mm.  of  calcium 
may  absorb  60  %  of  the  beam  the  second  mm. 
will  absorb  but  45  %  of  the  emergency  beam. 
This  is  due  to  the  production  of  a  character- 
istic radiation  by  the  calcium. 

With  increasing  thickness  all  bodies  of  the 
same  density  become  less  penetrable.  Dense 
substances  have  greater  absorptive  power 
mass  for  mass  than  light  substances. 

The  penetrability  of  a  body  depends  not 
only  upon  the  facts  given,  but  also  upon  the 
variety  of  x-rays  used.  The  atomic  weight  of 
zinc  is  about  half  of  that  of  tin  and  zinc  is 
more  penetrable  than  tin  to  medium  or  hard 
rays.  With  soft  rays  on  the  contrary  the 
difference  in  penetrability  will  become  less 
and  with  very  soft  rays  titi  will  be  more  pene- 
trable than  zinc. 

There  are  two  groups  of  chemical  sub- 
stances, v/hich  are  of  interest  to  the  roentgen- 
ologist in  reference  to  their  penetrability : 
first,  the  organic  structures  of  the  human  body 
and  animals,  which  consist  almost  completely 
of  carbon,  nitrogen,  hydrogen,  and  oxygen  and 
therefore  elements  of  small  atomic  weight, 
and  secondly,  the  inorganic  salts  of  calcium 
and  phosphorus  which  possess  a  much  higher 
atomic  weight  present  in  bones. 

The  absorption  by  bone  of  medium  rays  is 
only  slightly  greater  than  alumintun.  Accord- 
ing  to    Perthes    the    absorption   coefficient    of 


PROPERTIES  OF  X-RAYS 


79 


layers  of  water  1,  2,  3  and  4  cm.  is  respec- 
tively 0.540,  0.468,  0.424  and  0.390. 

The  penetrability  of  the  soft  parts  of  the 
human  body,  except  the  structures  which  are 
specifically  lighter  than  water  (lung  and  fat), 
and  that  of  water  is  almost  the  same,  in  other 
words  the  absorption  by  a  cubic  centimeter 
of  human  tissue  is  equal  to  that  of  a  cubic 
centimeter  of  water.  Lung  and  fat  are  more 
penetrable  than  water.  One  cm.  of  human 
tissue  absorbs  from    30  to  90%  of  x-rays. 

The  effect  of  the  roentgen  rays  diminishes 
rapidly  as  they  pass  beneath  the  surface.  In 
using  a  medium  tube,  only  sixty  per  cent 
arrives  at  one  centimeter  depth,  thirty 
to  forty-five  per  cent  reaches  two  centimeters 
depth,  and  twenty  to  thirty  per  cent,  is  present 
at  three  centimeters  depth.  With  the  use  of 
a  hard  tube,  however,  the  decrease  in  intensity 
occurs  more  slowly.  The  decrease  in  intensity 
may  be  made  to  take  place  more  slowly  by  the 
use  of  interposed  metals,  for  instance,  sheets 
of  aluminum. 

4.  Biological  effects. 

All  living  cells  are  sensitive  to  a  greater 
or  less  degree  to  the  x-rays.  This  biological 
eftect,  depending  on  the  intensity  of  exposure 
and  the  amount  of  absorption  by  the  cells,  will 
cause  either  stimulation,  retardation  in  growth 
or  complete  destruction. 

5.  Chemical  effects. 

Besides  the   bromide    of    silver,   there   are 


other  substances,  as  selenium,  iodine,  mercury 
compounds  and  ordinary  glass,  which  are  pro- 
foundly influenced  by  x-rays.  The  electric 
resistance  of  selenium  gradually  diminishes 
through  the  radiation.  The  iodine  and  mer- 
cury compounds  are  changed  from  soluble  to 
insoluble  salts  by  the  radiation  so  that  in  the 
solution  of  the  former  a  sediment  of  the  in- 
soluble salt  is  formed.  A  continuous  exposure 
to  the  ray  changes  the  color  of  certain  min- 
erals as  platino-barium  cyanide.  This  change 
of  color  in  platino-barium  cyanide  from  a 
yellow  green  to  yellow  brownish  red  is 
utilized  as  will  be  shown  later  as  a  color  reac- 
tion to  estimate  x-ray  intensity.  Ordinary 
glass  turns  yellow  under  the  influence  of  the 
rays,  while  crown  glass  turns  violet.  This 
discoloration  takes  place  when  the  tube  has 
been  used  for  any  length  of  time  and  is  not 
the  same  as  that  due  to  deposit  of  metal 
on  the  glass,  such  as  is  produced  by  inverse 
current  or  disintegration  of  the  target. 

6.  Ionization. 

By  this  is  meant  the  property  of  the  rays 
to  discharge  electrically  charged  bodies.  This 
effect  occurs  only  when  these  bodies  are  sur- 
rounded by  air  or  another  gas,  for  the  x-rays 
make  this  air  or  gas  electrically  conductive. 
They  do  this  by  disrupting  the  atom — sep- 
arating the  fast  moving  electron  from  the  slow 
positive  remainder. 


CHAPTER  X. 
THE  PRODUCTION  OF  X-RAYS. 

The  production  of  x-rays  depends  upon  the 
following  features : 

1.  The  disintegration  of  the  atom  and  the 
production  of  electrons. 

2.  The  acquisition  by  the  electrons  of  high 
velocity  by   electric   force. 

3.  Focusing  or  concentration  of  the  electron 
stream  by  the  cathode  terminal. 

4.  Production  of  a  sudden  velocity  change 
by  means  of  an  anodal  terminal. 

( 1 )  In  the  Crookes'  or  gas  tube,  in  which  a 
high  but  not  complete  vacuum  exists,  the  elec- 
trons are  obtained  by  disruption  of  the  resi- 
dual gas  by  the  high  electric  field. 

In  the  Coolidge  or  electron  tube,  in  which  a 
complete  vacuum  exists,  the  electrons  are 
secured  by  heating  a  tungsten  filament. 

(2)  A  high  velocity  is  imparted  to  the  elec- 
trons in  both  tubes  by  high  voltages  impressed 
across  the  terminals  of  the  tube. 

(3  )  In  the  gas  tube  the  concentration  of  the 
cathode  stream  to  a  point  is  secured  by  the 
design  of  a  concave  cathode  as  already  indi- 
cated. 

Aluminum  is  commonly  utilized,  as  a  cath- 
ode because  it  does  not  disintegrate,  emits  elec- 
trons with  ease  and  has  high  heat  conductivity. 

By  diminishing  the  size  of  the  cathodal  elec- 
trode, the  penetration  of  the  resulting  x-rays 
is  increased.  X^ arrowing  the  space  between 
the  cathode  and  the  glass  wall  and  withdraw- 
ing the  cathode  into  the  cylindrical  glass  ex- 
tension in  which  it  is  placed  have  the  same 
efifect. 

In  the  electron  tube  the  concentration  of  the 
cathode  stream  is  secured  by  an  electrostatic 
field  produced  by  means  of  the  molybdenum 
collar. 

(4)  The  velocity  change  of  the  cathode 
stream  is  produced  by  a  barrier  of  metal 
(tungsten,  platinum  or  iridium)  which  con- 
stitutes the  anode  or  target  of  the  tube. 

[80] 


The  intensity  of  the  resulting  radiatio*  de- 
pends on  the  constitution  of  the  target.  If  the 
intensity  of  radiation  of  platinum  is  con- 
sidered to  be  100,  tungsten  is  91,  molybdenum 
is  50,  and  nickel  is  30. 


Fig.  96. — The  distribution  of  x-rays  in  the  active 
hemisphere.  The  intensity  reaches  its  maxi- 
mum in  a  direction  about  60°  from  the  normal 
(6).  The  fall  in  intensity  from  60°  to  50°  is 
very  marked.  Actually  the  ra3rs  are  given  ofif 
from  the  back  of  the  target  as  well  as  the  front. 


From  the  target  the  x-rays  radiate  in  all  di- 
rections in  straight  lines  through  an  arc  of  one 
hundred  and  eightv  degrees.  The  rays  are  not, 
however,  evenly  distributed  upon  all  surfaces 
of  the  hemisphere  of  the  bulb.  The  most 
intense  radiations  are  about  the  central  bundle 
and  at  an  angle  of  thirty  degrees  to  the  cathode 
stream  at  the  point  of  impact  upon  the  target. 

An  x-ray  tube  correctly  activated  and  free 
from  inverse  is  separated  b_v  the  anti- 
cathode,  into  two  sharply  defined  hemispheres, 
the  active  half,  in  front  of  this  target,  fluor- 
escing a  light  green,  while  the  inactive  one 
behind  is  relatively  dark.  In  a  correctly  ener- 
gized tube  the  zones  are  sharply  bordered. 

A  tube  with  low  vacuum  is  called  soft, 
one  with  high  vacuum  hard.  A  hard  tube 
oft'ers  a  higher  resistance  to  the  passage  of 
the  current  and  requires  a  higher  potential  to 


THE  PRODUCTION  OF  X-RAYS 


81 


energize  it  and  produces  rays  of  higher  pene- 
trating power  which  are  called  hard  rays.  A 
soft  tube  produces  rays  of  low  penetrating 
power,  called  soft  rays.  The  hardness  of  the 
x-rays  is  entirely  dependent  on  the  maximum 
]iotential  difference  between  the  electrodes  of 
the  bulb,  in  other  words,  the  impressed  vol- 


Fic.   97. — The   vacuum   is   so   low   that   the   cathode 
stream  is  not  focused. 

tage.     This  potential  difference  may  be  con- 
trolled in  several  ways. 

1.  By    varying    the    characteristics    of    the 
tube : 
A.  \'acuum. 

The  higher  the  vacuum,  the  higher  the  vol- 
tage necessary  to  generate  x-rays  and  the 
higher  the  resulting  rav. 


B.  Electrode. 

The  tube  is  made  harder  by : 

(1)  Drawing    the    electrodes    closer    to 

each  other. 

(2)  Diminishing  the  size  of  the  cathode. 

(3)  By  withdrawing  the  cathode  terminal 

into  the  neck  of  the  tube. 

(4)  By    diminishing    the    sjjace    between 

the  cathode  and  the  glass. 


Fig.  99. — A^ery  low  vacuum  tube.  Note  the  absence 
of  sharph'  marked  zones,  the  clearly  defined 
cathode  stream  and  a  track  of  fluorescence  in 
the  active  hemisphere  due  to  the  fluorescence  of 
the  slowly  moving  electrons. 

C.  Regulator. 

A  tube  in  which  hydrogen  gas  is  used  as  a 
reducing  means  is  harder  than  one  in 
which  air  is  used  for  reducing. 


2.  By      increasing      the      current      density 
through  the  tube. 


Fig.  98. — Fine  focus  medium  vacuum  tube.  Note 
the  intense  glow  behind  the  target.  The  cathode 
stream  is  visible.- 


Fig.  ioc- 


-Showing  cathode  stream  in  a  low  vacuum 
tube. 


82 


HARDENING    OF    GAS    TUBES 


Because  of  the  escape  of  occluded  gases 
from  the  electrodes,  there  is  usually  a  lowering 
of  the  vacuum  of  the  tube  after  its  first  ener- 


FiG.  lOi. — Medium  vacuum  tube.  Note  fine  cathode 
stream,  relatively  sharp  focus,  wing-shaped  halo 
at  cathode  cup.  The  target  is  completely  re- 
flected. 

By  usage  the  vacuum  of  the  tube  is  in- 
creased. This  is  due  to  several  causes.  The 
most  potent  factor  is  the  pulverization  of  the 
target  which  combining  with  particles  of  gas 
is  deposited  on  the  glass  wall. 


Fig.  102. — Broad  focus,  medium  vacuum  tube.  The 
bright  point  below  the  bright  area  on  the  target 
is  a  reflected  image  of  the  focal  point. 

Other  factors  may  be  the  driving  of  the  gas 
into  the  glass  by  the  discharge,  and  the  chem- 
ical action  between  gas  and  glass. 


Fig.   103. — Fine   focus,  high  vacuum  tube. 


Fig.  104. — Reversed  polarity.  The  cathode  has  be- 
come the  anode.  The  area  of  fluorescence  is 
above  and  in  back  of  target. 


Fig.  ids. — Broad  focus,  high  vacuum  tube. 


APPEARANCE   OF   ACTIVATED    GAS    TUBE 


83 


The  electrostatic  charging  of  the  walls  of 
the  tube,  especially  about  the  cathode  results 
in  a  retention  of  the  gas  content  but  by  the 
heating  of  the  tube  this  retained  gas  is  re- 
leased. In  a  tube  normally  energized  an  equil- 
ibrium is  thus  maintained  and  the  vacuum  re- 
mains fairly  constant.  If  the  current  passing 
through  the  tube — does  not  heat  the  tube,  the 
electrostatic  charging  will  result  in  elevation 
of   the   vacuum.      But   if   the   tube  is   heavilv 


The  best  method  of  studying  the  phenomena 
in  an  activated  tube  is  to  photograph  it, 
by  means  of  a  pin  hole  camera  by  the  light 
furnished  by  the  energized  tube  itself.  Such 
a  photograph  discloses  more  than  is  apparent 
to  the  eye.  There  is  a  division  of  the 
glass  bulb  into  two  zones,  one  in  front  of 
the  target,  brightly  illuminated,  and  one 
behind,  which  is  relatively  dark,  with  the 
exception  of  a  greater  or  lesser  glow  about 


Fig.  io6. — The  tube  is  too  low  for  the  production  of  x-rays.     The  bluish  glow  of  the  ionized  gas  is 
shown  behind  the  target. 


energized  for  too  long  a  period,  a  marked 
lowering  of  the  vacuum  will  take  place.  Re- 
versal of  the  polarity  raises  the  vacuum. 

The  discoloration  of  the  active  half  of  the 
tube  takes  place  with  normal  usage  and  does 
not  affect  the  x-ray  output  but  the  pulveri- 
zation of  the  target  with  metallic  deposit  on 
the  glass  absorbs  a  certain  quota  of  the  rays. 
Hence,  reversing  the  polarity,  which  causes 
marked  sputtering  should  be  avoided. 

As  the  tube  hardens,  the  color  changes  to 
a  light  gray  green,  the  division  zone  becomes 
indistinct  and  the  hemispheres  lack  contrast. 


the  accessory  anode.  The  cathode  shows  its 
brightly  glowing  concave  surface.  The  stem 
and  the  glass  extension  in  which  it  is  set  are 
dark.  In  medium  and  low  vacuum  tubes  a 
fan-shaped,  illuminated  area  coming  from  the 
cathode  is  visible. 

The  cathode  stream  can  be  recognized 
by  the  eye  only  in  very  soft  tubes,  but  is  ap- 
parent in  the  photograph  in  all  except  very 
hard  tubes.  The  luminosity  is  due  to  the 
slowly  moving  electrons  which  impinge  upon 
the  gas  molecules  and  cause  them  to  fluor- 
esce.    This  phenomenon  may  be  seen  in  low 


•84 


PHOTOGRAPHY   OF   FOCAL   POINT   OF   TARGET 


vacuum  tubes  as  a  stream  of  electrons  extend- 
ing from  the  target  to  the  glass  wall.  The 
brilliantly  lit  area  on  the  target  represents  the 


Fig.  107. — Fine  focus  medium  vacuum  tube,  run  at 
normal  pressure  the  target  completeb'  utilizes 
the  cathodal  discharge. 

point  of  impact  of  the  cathode  stream.  This 
focal  spot  grows  larger  and  brighter  as  the 
-Stream  broadens.  In  front  of  it  is  a  glowing 
area — the  reflection  from  the  focal  point. 


A  reversed  image  of  the  cathode  cup  may 
be  seen  immediately  above  the  cathode.  This 
consists  of  an  illuminated  ring,  corresponding 
to  the  base  of  the  cone  of  the  cathode  stream, 
and  a  bright  center  corresponding  to  the  focus 
of  the  cathode  ray  bundle. 

Photographic  studies  of  the  activated  tube 
permit  the  determination  of  the  sharpness  of 
the  focus,  its  size  and  stability.  A  fluorescent 
screen  may  be  used  instead  of  a  plate  for  rapid 
tests.  The  study  of  the  focal  spot  has  an  im- 
portant bearing  on  the  sharpness  of  the  shadow 
cast  and  upon  the  amount  of  electrical  energ}^ 
the  tube  is  capable  of  consuming  for  the 
production  of  x-rays  without  disintegration  of 
the  target.  The  focal  spot  is  oval  in  shape, 
due  to  the  angular  inclination  of  the  target. 

These  photos  show  that  when  the  vacuum 
is  relatively  low.  the  target  completely  utilizes 
the  cathodal  energy  and  the  fine  focus  of  the 
stream  may  be  maintained.  Under  such 
potential  no  indirect  rays  are  produced. 


Fig.  108. — Fine  focus,  medium  vacuum  tube,  energized  at  abnormally  high  pressure  with  "  sputtering." 
■"  Sputtering "  of  the  tungsten  target,  results  in  metallic  deposit  on  the  glass  walls.  Platinum  "  sput- 
ters "  more  than  tungsten  and  though  the  intensity  of  the  resulting  radiation  is  somewhat  greater  than 
of  tungsten,  still  the  latter  metal  is  superior  as  a  target  because  of  its  high  degree  of  heat  conduc- 
tivity which  permits  very  sharp  focusing  of  the  cathode  stream.  This  metallic  deposit  on  the  glass 
wall's  is  responsible  for  the  rapid  hardening  of  the  tube  because  of  its  great  gas  absorptive  power.  It 
'.is  also  responsible  fcr  a  diminution  of  output  of  the  soft  rays 


FOCAL  POINT  OF  TARGET 


85 


In  high  vacuum  tubes,  the  glass  and  metal 
parts  of  the  tube  give  off  x-rays  and  the  in- 
tensitv  of  these  indirect  rays  may  be  very 
great  in  very  high  tubes. 

To  maintain  a  small,  sharp,  immobile  focus, 
a  tube  of  proper  size  (not  too  large)  and  of 
proper  vacuum  (not  too  high)  should  be  ener- 
gized with  a  sufficient  discharge  current  of 
the  proper  quality  and  the  inverse  suppressed. 

The  focal  point  of  the  target  is  deserving  of 
consideration  because  it  is  the  appreciation 
both  of  its  significance  and  variation  which 
makes  for  good  radiography.  The  definition 
of  shadow  structures  and  their  sharp  differ- 
entiation from  each  other  where  differences 
in  tissue  density  exist  depends  considerably 
on  the  size  of  the  focus.  The  focal  point 
should  be  as  small  as  is  consistent  with  the 
maximum  x-ray  output.  The  energy  input 
must  be  evenly  distributed  over  the  focal  spot 
while  the  heat  must  be  carried  off  rapidly. 
The  focal  point  tends  to  increase  in  size 
(Gotch)  : 


1.  In  tubes  of  large  diameters. 

2.  In  tubes  of  high  vacuum. 

3.  In  tubes  which  are  powerfully  energized. 

4.  In  tubes   in   which    an    unusual    degree 
of  electrostatic  charge  exists  on  the  glass  wall. 


Fig.    1 10. — Pinhole   camera    for   Roentgenograms   of 
Coolidge  tube.     (Coolidge.) 

The  focal  point  must  be  constant  in  its  posi- 
tion. A  variable  or  movable  focal  point  may 
be  due  to 

1.  JNIagnetic  deviations  of  the  cathode 
stream,  due  to  too  close  proximity  of  the  tube 
to  energizing  apparatus. 

2.  A  badly  constructed  tube  with  loose 
target  or  cathode. 


=] 


Fig.  109. — Diagrammatic  representation  of  the 
shadows  of  a  metallic  object  cast  by  a  beam  of 
rays  emanating  from  a  sharp  focus  (single 
point),  a  focus  of  i  mm.  in  diameter  and  a  focal 
spot  of  5mm.  The  object  is  placed  at  the  half 
distance  from  the  recording  surface,  20  cm.  The 
distortion  and  loss  of  definition  becomes  pro- 
gressively greater  as  the  size  of  the  focal  spot 
increases.  The  shadow  cast  by  the  sharp  focus 
would  have  a  diameter  of  2  mm.  and  be  of 
even  density.  The  shadow  cast  by  the  ray  from 
the  I  mm,  focus  would  have  2  zones  an  inner 
dense  and  having  nearly  the  diameter  of  the 
object  and  an  outer  less  dense.  The  total 
shadow  being  a  distortion.  The  shadow  cast 
by  the  ray  from  the  s  mm.  focus  shows  still 
greater  distortion.  The  penumbra  is  light,  the 
center  relatively  dense.     (Rosenthal.) 


Fig.  III. — Roentgenogram  of  Coolidge  tube  indicat- 
ing the  emission  of  x-rays  from  the  entire  target 
and  stem.     (Coolidge.) 


86 


RADIOGRAPH  OF  COOLIDGE  TUBE 


3.  Faulty  connections  whereby  the  target  is 
not  connected  to  the  accessory  anode. 

4.  When  an  alternative  gap  exists  in  the 
circuit  which  is  allowed  to  spark. 

5.  Marked  and  frequent  changing  of  the 
energizing  current  during  exposure. 

6.  Considerable  quantities  of  inverse. 

COOLIDGE  TUBE 

In  this  tube,  as  in  the  gas  tube,  the  cathode 
stream  is  a  cone  with  its  apex  at  the  target. 
This  result  is  obtained,  because  the  molybde- 
num cylinder  bears  a  negative  charge  and  re- 
pels electrons  in  their  flight.  The  position  of 
the  cylinder  determines  whether  the  stream 
strikes  the  target  at  a  point  or  at  a  small  area 
and  whether,  therefore,  the  tube  is  "  fine 
focus  "  or  "  broad  focus." 

Under  normal  working  conditions  there  is 
no  apparent  movement  of  the  focal  point  in  a 
Coolidge  tube  except  in  exposures  under  stress, 
as  for  instance  when  100  mills,  with  1  inch 
gap  or  20  mills,  with  9  inch  gap  are  used. 

The  active  Coolidge  tube  may  be  studied 
photographically  by  means  of  its  own  radia- 
tion bv  a  pin-hole  opening  in  a  lead  box.  The 
camera  used  by  Coolidge  has  a  diaphragm. 
0.020  inches  in  diameter;  the  distance  from 
the  long  axis   of   the   tube  to  the   pinhole   is 


Fig.  112. — Pin  hole  camera  Roentgenogram  of  front 
and  back  of  target,  showing  the  emission  of 
x-rays  from  all  points,  except  working  face, 
to  be  of  same  intensitj'.     (Coolidge.) 

15  in.,  and  the  distance  from  the  pinhole  to 
the   photographic   plate    is    5   inches.      In   the 


length  views  of  the  target  the  tube  was  so 
placed  that  the  neck  of  the  target  was  directly 
opposite  the  pinhole  (see  Fig.  110).  The 
plate  was  in  a  closed  box  made  of  lead  J/s  inch 
thick.  The  tube  was  energized  by  a  voltage 
corresponding  to  a  7  in.   spark  gap  between 


Fig.  113. — The  emission  of  rays  from  points  other 
than  the  focal  spot  is  less  marked  when  lower 
voltages  are  used  (lower  figure)  than  when 
higher  voltages  are  used  (upper  figure). 

points  with  a  current  of  5  milliamperes.     The 
plates  were  developed  for  ten  minutes. 

A  radiograph  made  with  a  standard  medium 
focus  tube,  operating  under  such  conditions, 
shows  that  the  entire  target  ( both  front  and 
back ) ,    including   the    molybdenum    stem    and 


Fig.  114, — W'we  screen  test  with  fine  focus  tube. 

the  adjacent  end  of  the  iron  support  tube, 
gives  off  roentgen  rays  and  must,  therefore, 
be  bombarded  by  cathode  rays.  These  un- 
desired  radiations  are  less  when  the  tube  is 


FOCAL  POINT  TESTS 


87 


energized  by  low  voltages.  The  radiation 
from  the  back  is,  however,  but  one-ninth  of 
the  radiations  from  the  front  of  the  target. 
By    proper    diaphragming,    these    rays,    how- 


FiG.   115. — Wire  screen  test  with   broad   focus  tube. 

ever,  do  not  appear  to  materially  afifect  such 
radiographic    definition,    as    obtained    by    the 


Coolidge   tube.      Other    ways   of    diminishing 
these  aberrant  rays  are : 

1.  By  a  hood  over  the  anticathode. 

2.  By  the  use  of  a  tungsten  button  set  in 
copper. 

3.  Placing  the  anticathode  at  right  angles  to 
the  long  axis  of  the  tube. 


Fig.    1 17. — Metallic    Iris    diaphragm. 

A  simple  method  of  testing  the  size  and 
mobility  of  the  focus  is  by  the  use  of  a  piece 
of  wire  netting  of  one  centimeter  mesh  held 
equidistant  (eight  inches)  from  the  target  and 
from  the  recording  surface.  The  sharp- 
ness of  the  resulting  shadows  will  indicate  the 
condition  of  the  focal  point.  (Figs.  114-115). 
The  focal  spot  itself  may  be  studied  radio- 
graphically  by  a  pin  hole  opening  in  a  lead 
plate,  placed  equidistant  from  tube  and  photo- 
graphic plate. 


Fig.  116. — Primary,  scattered  and  secondary  radia- 
tions. E — Leadplate.  D — Object.  B — Record- 
ing surface.     (L.-G.  Cole.) 


Fig.  iiS. — Slit  and  rectangular  diaphragm. 


88 


DIAPHRAGMS 


Fig.  iiy. — Simple  lead  diaphragm  placed  half  way 
between  target  and  recording"  surface.  The  sec- 
ondary rays  from  the  walls  of  the  tube  reach 
the  plate,  however,  giving  a  penumbra  of  partial 
illumination. 


Fig.   120. — The  diaphragm  in  close  proximity  to  the 
tube  is  more  effective  than  when  placed  in  close 

proximity  to  the  object. 


t^///.-^'^/W/>.-x,J^:-.-.^>>^y.^-::Cy^^Xx^^^^ 


Fig.  121. — The  use  of  a  simple  cylinder  is  not  suffi- 
cient to  cut  off  the  secondary  radiations  from 
the  glass  wall  of  the  tube. 


Fig.  122. — The  use  of  a  cylinder  in  conjunction  with 
the  diaphragm  is,  however,  most  effective. 


Fig.  123. — Single  tubular  diaphragm  placed  between 
screen  (P)  and  object.  The  :  :condary  radia- 
tions from  certain  parts  of  the  object  A,  B,  C, 
and  D,  E,  F,  are  cut  off  with  the  resulting  in- 
crease in  definition.     (Shearer.) 


PRLMAkY  AND  SECONDARY  RAYS 


89 


PRIMARY  AND  SECONDARY  RAYS 

Two  kinds  of  rays  are  emitted  from  the  tar- 
get, one  heterosjeneous  and  the  other  charac- 
teristic   of    the    metal, — homogeneous.      The 


Fig.  124. — A  shows  a  plan  of  the  top  of  tubular 
grating  for  use  below  the  tube.  B.  shows  a  plan 
of  the  same  as  seen  from  the  side.  The  move- 
ment is  along  the  curved  track  Avhose  center  of 
curvature  is  at  the  anode. 

higher  the  atomic  weight  of  the  target,  the 
greater  the  quantity  of  heterogeneous  rays 
\\'ith  the  same  metal  the  softer  the  rays  gen- 
erated the  greater  the  quantity  of  characteris- 
tic rays. 

Secondary  Radiations.  When  the  primary 
x-ray  bundle  emanating  from  the  target  and 
consisting,  as  has  been  stated,  of  two  varieties 
of  rays,  the  heterogeneous  or  general  and  the 
homogeneous    or    characteristic,    strikes    any 


Fig.  125. — Potter-Bucky  diaphragm. 

substance,    there    are    generated    other    radia- 
tions.    These  are  of  three  varieties : 

1.  The  scattered  rays. 

2.  The  characteristic  rays   (which  are  true 
x-rays ) . 

3.  The    so-called    corpuscular    rays,    which 


are  negatively  charged  electrons,  moving  with 
a  velocity  equal  to  that  of  the  cathode  rays 
which  generated  the  primary  beam. 

The  latter  two  are  true  secondary  radia- 
tions. 

The  only  difference  between  the  primary 
and  the  scattered  x-rays  is  that  the  latter  have 
no  definite  course  but  radiate  in  all  directions 
and  thus  in  fluoroscopic  and  radiographic  work 
serve  only  to  blur  the  image  and  in  therapy 
intensify  the  effect  of  the  direct  ray.  It  is  the 
original  ray,  modified  by  absorption  and  dif- 
fusion by  the  medium  through  which  it  passes. 

Substances  differ  in  their  power  of  scatter- 
ing the  primary  rays  and  this  quality  they 
possess  in  proportion  to  their  atomic  weight. 


Fig 


126. — A  Bucky  grating  is  mounted  on  a  skeleton 
platform.  Ball  bearings  and  a  track  allow  the 
grating  to  move  in  a  linear  direction  along  the 
platform.  The  platform  itself  is  mounted  so 
that  it  may  move  on  another  track  at  ninety 
degrees  to  the  first.  Thus  the  grating  has  uni- 
versal motion  and  may  be  guided  in  the  square 
direction  above  described  bv  a  mechanism  at  the 
side."     (Potter.) 


Organic  matter  has  this  scattering  power  to  a 
greater  degree  than  such  metals  as  copper  or 
aluminum. 

Characteristic  Secondary  Radiations.  Every 
metal,  when  struck  by  a  beam  of  primary  x- 
rays  emits  secondary  x-rays.  The  qualities 
of  these  secondary  rays  depend  solely  on  the 
particular  metal  subjected  to  the  primary 
beam. 

These  secondary  radiations  are  homogene- 
ous in  quality  and  the  higher  the  atomic  weight 


90 


CHARACTERISTIC  RAYS 


of  the  element  from  which  they  are  emitted 
the  greater  their  penetrating  power,  whether 
the  metal  is  in  its  elemental  or  combined 
state. 


Fig.  127. — The  multiple  spark  gap,  consisting  of 
points  and  discs,  movable  independently  or 
together,  by  means  of  rods.  One  or  two  of 
these  points  may  be  sufficient  to  cut  out  the 
inverse.     (Hirsch.) 


Fig.  128. — Two  valve  tubes  in  x-ray  circuit. 

The    quantity    of    characteristic    secondary 
radiation   may   be    increased,    if   the   primary 


x-ray  bundle  is  generated  from  a  target  of 
the  same  metal,  as  is  used  for  the  generation 
of  the  characteristic  rays.  For  it  has  beeft  noted 
that  the  primary  x-ray  bundle  itself  is  partly 
of  homogeneous  rays,  characteristic  of  the 
metal  used  as  target.  Therefore,  to  generate 
a  maximum  amount  of  characteristic  second- 


C^Tr^lOt 


Fig.   I2g. — Triple  valve  tube  in  secondary  circuit  to 
cut    out    inverse. 

ary  radiations,  the  radiating  element  and  the 
target  should  be  of  the  same  metal  as  the  filter 
and  the  primary  beam  contain  its  maximum 
amount  of  homogeneous  rays. 

If,  in  time  to  come,  therapy  is  to  be  done 
with  homogeneous  rays,  energization  of  the 
tube  b)'  higher  voltages  and  the  use  of  filters 
of  the  same  material  as  the  target  will  be 
necessary. 

The  scattered  and  characteristic  radiations 
which  constitute  the  greater  part  of  the  sec- 
ondary radiations  may  arise  either  from  the 
tube  itself,  from  the  air  and  frotn  the  object 
struck.  These  may  be  more  or  less  si:ccess- 
fuUy  eliminated  b}^  the  use  of  diaphragms, 
cylinders,  or  composite  tubular  diaphragms 
so  constructed  and  moved  as  to  neutralize  their 
ow'n  shadows. 

Diaphragms:  A  diaphragm  of  lead  should 
be  placed  as  near  to  the  glass  of  the  tube  as 
possible.  Its  effectiveness  depends  on  its  close 
proximity  to  the  target  and  the  size  of  its 
opening.  Its  effect  may  be  enhanced  by  the 
use  of  cylinders  of  metal.  The  effect  of  this 
depends  upon  the  diameter  of  its  upper  end, 
the  length  of  the  cylinder,  the  diameter  of  the 
lower  end,  and  the  absorption  power  of  the 


VALVE-TUBES 


91 


metal.  In  order,  however,  to  increase  the  ex- 
tent of  the  field  covered  by  the  rays,  cones 
have  come  in  use.  The  upper  end  of  these 
have  permanent  diaphragms,  the  lower  are  ex- 
panded according  to  the  necessities  of  the  ex- 
amination.    (Figs.   119-122.) 

It  is,  however,  the  rays  which  arise  from 
the  object  struck  by  the  primary  bundle  which 
present  the  greatest  problem  in  eradication. 
Bucky's  diaphragm,  consisting  of  a  multiple 
tubular  diaphragm  is  an  effective  means  of 
combating  these  rays  but  has  the  disadvantage 
that  the  shadow  of  the  grating  itself  is  seen 
on  the  recording  surface  and  more  or  less 
distortion  results  because  of  the  distance  of 
the  object  from  the  recording  surface  since 
the  screen  is  interposed  between  it  and  the 
object.     (Fig.  123.) 

Potter  has  constructed  an  instrument  on 
the  Bucky  principle,  but  placed  between  tube, 
and  object  which  by  movement  effaces  the 
shadow  of  the  grating.  (Figs.  124,  125,  126.) 
This  device  is  based  on  the  principle  that  a  strip 
of  lead  placed  on  edge  may  be  moved  across  a 
sensitive  plate  during  constant  exposure,  if  the 
strip  be  kept  so  tilted  during  its  passage  over 
the  plate  that  its  face  is  constantl)'  in  the  plane 
of  the  rays.  In  the  Potter  diaphragm  there 
are  two  sets  of  parallel  lead  strips,  set  at  right 
angles  to  each  other,  making  a  grating.  These 
are  moved  along  the  diagonal  of  the  squares  so 
formed.  The  grating  is  placed  so  that  both 
upper  and  lower  edges  are  in  the  circumfer- 
ence of  spheres  whose  common  center  is  the 
focal  point.  Thus  the  planes  of  all  the  strips 
of  the  grating  pass  through  the  focus.  By 
means  of  ball  bearings  along  a  curved  track, 
the  spherical  grating  is  made  to  move  to  and 
fro  and  is  always  equidistant  from  the  focus. 

For  fluoroscopy  fine  definition  over  a  lim- 
ited field  may  be  obtained  by  a  single  tubular 
diaphragm  placed  between  the  object  and 
screen. 

Inverse  Current 

Inverse  discharges  entering  the  tube  gener- 
ate aberrant  rays  which  serve  to  cause  loss  of 
definition. 


Tubes  which  have  inverse  exhibit  a  char- 
acteristic appearance.  Because  of  the  emana- 
tion of  cathode  rays  from  the  anticathode  and 
anode  many  rings  of  fluorescence,  and  flitting, 
fluttering  green  stripes  are  visible.  Then  there 
is  a  striped  and  spotted  illumination  of  the 
glass  wall  badv  of  the  anodal  half  of  the 
tube,  the  metal  parts  of  the  anticathode  being 
shadowed  on  the  glass  wall. 

Inverse  discharges  may  be  prevented  in  sev- 
eral ways.  The  insertion  of  an  air  gap,  con- 
sisting of  point  and  disc,  the  point  being  made 
negative,  and  naturally  offering  great  resist- 
ance, will  prevent  the  passage  of  current  in  the 
wrong  direction,  but  the  loss  of  actual  voltage 
in  this  method  is  too  great. 

Tubes  of  various  types  known  as  valve 
tubes  have  been  constructed  for  the  purpose 
of  eliminating  the  results  of  inverse.  They 
are  all  low  vacuum  tubes,  having  one  large 
and  onte  small  electrode,  so  that  there  is 
marked  resistance  to  the  passage  of  current  in 
one  direction. 

In  one  form  a  small,  rod-like  electrode  is 
fixed  within  a  glass  tube.  The  other  electrode 
is  a  large,  spiral  valve.  Good  valve  action  is 
thus  obtained.  The  tube  must  be  so  placed  in 
the  secondar}'  current  circuit  that  it  is  between 
the  cathode  of  the  tube  and  the  cathode  of  the 
coil,  and  so  that  the  small  electrode  becomes 
the  anode. 

All  valve  tubes  have  regulating  devices,  for 
efficient  valve  action  only  takes  place  when 
the  vacuum  is  low.  The}'  are  usually  used 
two  or  three  together.  (Fig.  129).  In  some 
types  of  tubes  an  impedence  winding  consist- 
ing of  a  small  iron  core  wound  with  wire  is 
placed  between  target  and  accessory  anode. 
This  prevents  inverse  because  of  resistance 
offered  by  the  self-induction.  The  Coolidge 
tube  acts  as  its  own  valve  tube  as  long  as  the 
temperature  of  the  target  does  not  exceed  that 
of  the  cathode.  A  special  tube  built  on  the  same 
principle  and  called  a  kenotron  is  being  used 
for  this  purpose.  With  a  properly  constructed 
transformer,  the  kenotron  may  be  used  in- 
stead of  a  mechanical  rectifier. 

If   a   Coolidge   tube   can   be    kept   below   a 


92 


THE  OSCILLOSCOPE 


certain  temperature  (water,  air  or  oil 
cooling),  a  rectifying  device  becomes  unneces- 
sary and  the  high  tension  alternating  current 
may  be  used  directly  for  energizing  it. 
But  since,  by  the  use  of  such  means  of  ener- 


D    C 


a)  The  aluminum  rods  are  separated  by  an  air 
space  of  2  mm.  In  some  forms  of  oscilloscope  a 
thin  plate  of  glass  is  placed  between  the  ends  of 
the  rods  to  prevent  sparking. 


b)  The  oscilloscope  when  placed  in  an  x-ray  circuit 
free  from  inverse  will  show  a  bluish-violet  light 
over  the  negative  pole,  the  positive  pole  will  be  dark. 


c)  If  inverse  is  present,  the  anodal  end  also  shows 
this  bluish-violet  light  which  will  involve  more  or 
less  of  the  rod  depending  on  the  quantity. 


d)    Same,  showing  less  inverse. 

Fig.  130. — Oscilloscope  (a),  its  illumination  under 
normal  conditions  (b),  and  w-hen  inverse  is 
present   (c)    and    (d). 

gization  only  one-half  the  wave  is  util- 
ized by  the  tube,  it  is  essential  that  the  trans- 
former be  especially  wound  for  this  purpose, 
if   the   maximum   efficiency   is  to  be  attained 


and  the  measurement  of  the  potential  be  possi- 
ble. For  the  inverse  voltage  may  be  higher 
than  the  half  wave  going  into  the  tube  X^^S- 
46)  and  thus  the  sparking  across  the  gap, 
which  would  be  due  to  this,  would  be  no  index 
of  the  amount  passing  into  the  tube.  Besides 
this  there  would,  with  the  ordinary  trans- 
former, be  a  considerable  strain  on  its  insula- 
tion. 

Such  an  energizing  apparatus,  however, 
would  have  the  advantage  of  the  elimination 
of  all  moving  parts,  simplicity  of  control  and 
steadiness  of  operation.  The  utilization  of  ex- 
tremely high  voltages  becomes  practical  with 
such   a   combination. 

Inverse  may  be  detected  by  the  oscilloscope. 
(Fig.  130).  It  consists  of  a  cylindrical  tube, 
having  two  rod  electrodes  of  aluminum,  en- 
closed in  glass  sleeves.  The  ends  of  the  elec- 
.trodes  are  1-2  mm.  apart.  The  vacuum  of  the 
tube  is  four-one-hundredths  of  the  original  air 
pressure.  Connected  in  series  with  the  x-ray 
tube,  the  negative  electrode  is  surrounded  by  a 
bluish  violet  glow,  which  increases  in  length 
and  strength  in  proportion  to  the  current,  while 
the  anode  remains  dark.  (Fig.  130-b).  If 
inverse  is  present  the  anodal  end  is  also  thus 
illuminated.  (Fig.  130-c  and  d).  Such  a 
tube  has  been  constructed  marked  with  a 
scale  graduated  from  the  center  towards  both 
ends.  In  this  way  the  extent  of  the  glow  may 
be  measured  and  an  idea  thus  obtained  of  the 
maximiun  value  of  the  impulses  of  the  second- 
ary current.  For  by  means  of  a  rotating  mir- 
ror the  imptilses  which  give  rise  to  this  glow 
may  be  isolated,  studied  and  photographed, 
if  the  rotations  of  the  mirror  are  so  graduated 
that  the  image  is  stationary. 


CHAPTER  XI 
THE  [MEASUREMENT  OF  X-RAYS 

The  character  of  the  primary  ray  must 
needs  be  measured  with  regard  to 

1.  QuaHty   (penetrability). 

2.  Quantity  (intensity). 

Methods  of  measuring  the  quality  of  the 
x-rays. 

1.  By  measuring  the  maximum  potential 
required  to  generate  the  rays. 

2.  By  measuring  the  penetrating  quality  of 
the  ray  itself.  A  comparative  study  of  the 
percentage  of  the  particular  ray  absorbed  by 
media  having  certain  definite  characteristic 
qualities  is  estimated  by  the 

a)  Comparative  absorptive  efifect  of  suc- 
cessive layers  of  certain  materials,  as 
aluminum  and  silver. 


b)    Absorptive    effect   of   thicknesses   of 
similar  metal  or  water. 
3.  By  measuring  the  wave  length  of  the  ray. 

1.  By  Measuring  Maximum  Potexti.\l 
Measurement  by  Volliiictcr.  The  relation- 
ship between  the  cathode  stream  and  the  x-ray 
it  produces  has  already  been  indicated.  The 
higher  the  speed  of  the  exciting  cathode 
stream,  the  more  penetrating  or  harder  the 
ray.  Since  the  speed  of  the  cathode  stream 
is  dependent  upon  the  e.  m.  f.  applied  to 
the  tube,  or  the  potential  difference  between 
the  terminals,  then  the  measurement  of  this 
voltage  is  an  index  to  the  quality  of  the 
ray.  The  potential  may  be  accurately 
measured  by  means  of  a  voltmeter  in  conjunc- 
tion with  a  special  potential  coil  located  in  the 
transformer  if  the  latter  be  of  sufficient  size  as 


T.^BLE 

OF  Sp.\rking  Potenti.^ls  (Kaye) 

Gap 

Diameter  of  Balls 

Sp.\rk 

Needle  pts. 

0.5  cm. 

1  cm. 

2  cm. 

5  cm. 

cm. 

inch. 

A.  C.  volts  (Ma.x.) 

D.  C.  volts 

D.  C.  volts 

D.  C.  volts 

D.  C.  volts 

0.1 

,04 

1000 

5000 

5000 

5000 

5000 

0.2 

.08 

2000 

8000 

8000 

8000 

9000 

0.3 

.12 

4000 

11000 

11000 

11000 

12000 

0.4 

.16 

5000 

14000 

14000 

14000 

15000 

0.5 

.20 

6000 

16000 

17000 

17000 

18000 

0.6 

.24 

7000 

17000 

20000 

20000 

21000 

0.7 

.28 

8000 

18000 

22000 

23000 

24000 

0.8 

.31 

10000 

19000 

24000 

26000 

27000 

0.9 

.35 

11000 

20000 

26000 

29000 

30900 

1 

.39 

12000 

21000 

27000 

31000 

33900 

2 

.79 

24000 

24000 

36000 

48000 

57000 

3 

1.18 

34000 

26000 

42000 

5S000 

77000 

4 

1.58 

42000 

27000 

45000 

65000 

93000 

5 

1.97 

49000 

Brush  discharge 

47000 

71000 

105000 

■6 

2.36 

55000 

usually  occurs. 

Brush  discharge 

77000 

116000 

7 

2.76 

61000 

usually  occurs. 

82000 

125000 

•8 

3.15 

66000 

87000 

133000 

9 

3.54 

71000 

91000 

140000 

10 

3.94 

76000 

95000 

145000 

IS 

5.91 

102000 

Brush  discharge 

170000 

20 

7.9 

122000 

usually  occurs. 

190000 

30 

11.8 

170000 

40 

15.8 

220000 

Table  IV 

[S3] 


94 


KILO  VOLTMETER 


Sphere — Gap   Spark  Voltages 


Kilo-V. 

62.5  mm. 

Kilo-V. 

125  mm. 

10 

4.2mm 

20 

8.6 

30 

13.5 

14. 1mm 

40 

19.2 

19.1 

50 

25.0 

24.4 

60 

32.0 

30 

70 

39.5 

36 

80 

60.5 

42 

90 

73 

49 

100 

55 

120 

71 

140 

88 

160 

110 

180 

138 

62.5  mm.  =  2.46  inches. 
125  mm.  =  4.91  inches. 


With  very  large  gaps  the  shape  of  the  electrode  is 
immaterial. 

Table  V 


Inches  Gap  Between  Points  and  K.  V.  Necessary 
To  Obtain  It 


Inches 

K.  V. 

K.  V. 

Inches 

1 

20 

10 

3/5 

2 

30  1/2 

20 

1 

3 

40  1/2 

30 

1  3/5 

4 

50  1/3 

40 

2  2/5 

5 

60  1/4 

50 

3  1/2 

6 

70 

60 

4  4;  5 

7 

80  3/4 

70 

6 

8 

80  1/2 

80 

7  2/5 

9 

90  1/3 

90 

8  1/2 

10 

100 

100 

9  4/5 

110 

11 

120 

12  2/5 

regards  its  primary  and  secondary  winding 
make-up.  A  voltmeter  called  a  spark-meter 
may  be  connected  across  the  primary,^  and 
calibrated    and    corrected     for    the    various 


Table  VI 


Fig.  132. — Sphere  spintermeter,  standardized  by  the 
American  Institute  of  Electrical  Engineers.  The 
spheres  are  6214  mm.  in  diameter.  The  sparking 
distance  is  adjustable  by  means  of  a  fine  ad- 
justment. On  either  side  are  U  tubes,  filled  with 
distilled  water,  to  serve  as  a  resistance  in  the 
circuit  in  order  to  prevent  destructive  arcing 
of  the  spheres.  The  tubes  are  34  inch  in  diame- 
ter, of  such  a  length  that  there  is  in  each  about 
15  inches  of  water.  The  gap  should  be  measured 
at  the  point  where  there  is  intense  glow  about 
the  terminals  with  a  frequent  spark  across  the 
gap.  Both  the  supports  and  spheres  must  be 
kept  clean  and  dry.     (Coolidge.) 

loads  by  spark-gap  measurements.  Data 
furnished  by  this  means  cannot  be  ap- 
plied from  one  interrupterless  apparatus  to 
another. 

Mcasiireincnt  by  Equivalent  Spark  Gap. 
As  a  practical  means  for  determining  this 
voltage,    the    sparking    distance    of    varying 


"5 

I- 

2 


" 

— 

— 

— 





\— 

— 

' 

— 1 

1 — 

— 

— ■ 

- 

I 

~ 

r 

/• 

/ 

/ 

,/ 

^ 

, 

^ 

y 

^ 

J 

y 

/ 

/ 

y 

' 

/ 

/ 

/ 

/ 

/ 

^ 

/ 

f^ 

r^ 

^ 

f' 

" 

;=^ 

- 

=" 

' 

1 

_. 

■, 

60       00      -100      110      120 


Fig.  131. — Relation  between  kilovolts  and  spark  gap  between  points. 


SPARK-GAP  MEASUREMENTS 


95 


potentials  are  utilized.  An  air  gap  between 
points  is  commonly  used,  but  it  is  inaccurate, 
unless  standard  conditions  are  adhered  to.  It  is 
not  necessary  to  obtain  an  arc  or  flame  across 
the  terminals.  These  should  be  so  separated 
that  there  is  a  glow  with  an  occasional  spark- 
ing across.  With  the  same  voltage  a  longer 
spark  will  be  obtained  between  sharp  points 


British  Roentgen  Society  have  published  tables 
of  spark  length  and  corresponding  voltages 
for  direct  and  alternating  currents.    Table  IV. 


Fig.  133. — Bauer  Qualimeter.  The  two  horizontal 
plates  act  as  a  condenser.  The  vertical  plates 
(shaded)  are  immovable  and  between  them  there 
swing  the  two  wings,  one  of  which  carries  a 
pointer   (not  shown). 

than  between  blunt.  For  accurate  determina- 
tion, the  spark  lengths  should  be  measured 
between  balls  62.5  mm.,  in  diameter  according 
to  standardization  rules  of  the  A.  I.  E.  E. 
(Fig.  132.)  The  penetrating  power  or  hard- 
ness of  the  x-ray  is  proportional  to  the  square 
root  of  the  spark  gap. 

180,000  volts  should  give  rays  having  a 
penetration  of  the  gamma  rays  of  radium  C, 
which  is  only  one-half  absorbed  by  six  centi- 
meters of  lead.  X-rays  have  been  experimen- 
tally produced  with  voltages  as  low  as  200  to 
1,060. 

The   committee   on   standardization   of   the 


.  134. — Bauer  QuaUmeter,  showing  the  scale 
on  which  the  pointer  attached  to  the  movable 
wings  indicates  the  potential  of  the  high  tension 
current  in  terms  of  absorption  of  x-rays  by  I-IO 
mm.  of  lead.  The  instrument  must  be  hung  so 
that  it  is  always  in  the  vertical  position,  at  a 
minimum  distance  of  twelve  inches  from  any 
electrostatically  charged   substance. 


Fig.  135. — Benoist  Qualimeter.  The  central  disc  is 
of  silver  and  concentrically  disposed  about  it  are 
twelve  sectors  of  aluminum  from  i  to  12  mm. 
in   thickness. 

Mcasiirciiiciit  by  Static  Electrometer — - 
Bauer  Qualimeter.  Another  method  of  meas- 
uring the  potential  difference  between  the 
anode  and  cathode  and  of  translating  it  in 
terms  of  ray  penetration  is  by  means  of  the 
Bauer  Qualimeter.     (Figs.   133,  134.) 


96 


BAUER  OUALIMETER 


The  Bauer  Qualimeter  makes  use  of  a 
device  which  depends  on  the  fall  of  potential 
in  a  condenser.  It  consists  of  two  circular 
metallic  plates  with  an  air  space  between 
them    forming   a    condenser,    placed    above    a 


Fig.  136. —  Benoist  Penetrometer.  Radiographic 
Test.  Ttie  variously  darkened  sectors  are  com- 
pared to  the  central  area  and  the  matching  sec- 
tor indicates  the  penetration  of  the  ray  in  terms 
of  Benoist  units. 

static  electrometer.  This  electrometer  con- 
sists of  two  fixed  metallic  plates  between 
which  there  swings  on  a  pendulum  two  metal- 
lic wings,  fixed  on  a  common  axis.  When 
these   are   jointed   up  to   the   cathode   of   the 


Fig.  137. — Wehnelt  Qualimeter.  Here  the  silver 
foil  is  in  the  form  of  a  long  strip  and  the  alumi- 
num in  the  form  of  a  wedge.  The  aluminum 
wedge  moves  in  front  of  a  small  window.  Be- 
tween this  window  and  the  metals  is  placed  a 
small  platinobarium  cyanide  screen.  By  means 
of  a  rack  and  pinion  the  wedge-shaped  piece  of 
aluminum  is  moved  until  the  illumination  of 
the  windows  over  the  metals  is  even.  By  means 
of  a  small  hood,  placed  over  the  windows,  this 
measurement  may  be  made  in  daylight.  The 
pointer  indicates  the  degree  of  hardness  meas- 
ured in  Wehnelt  units. 


secondary  circuit,  the  plates  and  the  pendulum 
are  both  equally  charged,  and  the  repulsion 
which  is  produced  will  be  directly  proportional 
to  the  electrical  tension  in  the  circuit.  A 
pointer  attached  to  the  pendulum  passes  over 
a  suitably  divided  scale,  the  deviation  depend- 
ing upon  the  voltage  in  the  secondary' circuit. 

The  instrument  is  suspended  from  a 
bracket  so  as  to  be  always  in  a  vertical  posi- 
tion. It  is  unipolar  and  may  be  connected 
to  the  negative  terminal  of  the  coil  or  the 
cathode  of  the  tube. 

The  divisions  on  the  scale  correspond  to  the 
quality  of  the  rays  absorbed  by  lead  of  various 
thicknesses.  Thus,  1°  on  the  scale  corresponds 
to  x-rays  of  such  a  hardness  as  to  be  totally 
absorbed  by  1/10  millimeter  of  lead.     \\'hen 


Fig.   138. — Walter   Qualinieter, 

the  index  is  at  10°,  the  tube  should  be  emitting 
rays  capable  of  penetrating  9/10  (.9)  mm.  of 
lead  and  be  totally  absorbed  by  1  mm.  of  the 
metal. 

2.  By  Measuring  Penetrative  Quality  of 
THE  Ray 

(a)  Mcasurcincnt  by  Selective  Absorption. 
A  number  of  scales  have  been  constructed, 
based  on  the  selective  absorption  by  metals 
of  rays  of  varying  penetrability.  Thus, 
silver  and  other  metals  whose  atomic  weight 
is  about  100  do  not  absorb  the  rays  of  low 
penetrating  power  to  any  greater  degree  than 
the  highly  penetrating  rays,  while  the  absorp- 
tive power  of  aluminum  varies  with  the 
quality  of  the  rays,  the  soft  rays  being  ab- 
sorbed more  than  the  medium  or  hard. 

Thus  by  comparing  the  absorptive  power 
of   lavers   of   aluminum  to  that  of  a  certain 


BENOIST  AND  WALTER  METERS 


97 


fixed  thickness  of  silver,  as  judged  by  the 
fluorescent  power  of  the  emergent  ray,  a 
definite  scale  may  be  constructed. 

Roentgen  himself  was  the  first  to  apply  this 
principle  in  the  construction  of  a  scale.  He 
utilized  aluminum  and  platinum. 

Benoist  Penctrouictcr.  (Figs.  135,  136.) 
The  Benoist  penetrometer  consists  of  a  thin 
silver  disc  0.11  mm.  thick,  surrovmded  by 
twelve  numbered  aluminum  sectors  from  1  to 
12  mm.  thick,  placed  in  arithmetical  progres- 
sion. The  penetrability  of  the  ray  is  measured 
by  matching  on  a  fluorescent  screen  or  photo- 
graphic plate,  the  shadow  cast  by  the  silver 
disc  against  the  shadows  of  the  aluminum 
plates ;  the  thickness  of  the  matching  sector 
increases  with  the  hardness  of  the  rays.  (Fig. 
138). 

Walter  modified  the  Benoist  scale  (Fig. 
139)  by  using  six  aluminum  sectors  instead  of 
twelve,  combining  two  Benoist  fields  to  make 
one.  The  thickness  of  the  aluminum  in  the 
six  fields  of  this  scale  are  2.0,  2.4,  3.2,  4.4,  6.0 
and  8.0  mm. 

The  \A'ehnelt  meter  (Fig.  137)  is  similar  in 
principle  of  its  construction  to  the  Benoist, 
except  that  an  aluminum  wedge  is  used  instead 
of  stepped  sectors  and  the  silver  is  in  the  form 
of  a  strip. 

Both  these  methods  are  inaccurate  because 
silver  does  not  always  have  a  constant  trans- 
parency to  all  qualities  of  x-ray. 

(b)  Measurement  by  Complete  Absorption. 
There  are  several  scales  constructed  on  the 
basis  of  the  absorption  of  the  ray  by  various 
thicknesses  of  the  same  metal. 

Jl'alter  Scale 

This  consists  of  a  lead  plate,  two  milli- 
meters thick  and  twenty  centimeters  in  dia- 
meter, perforated  by  eight  holes,  each  six 
millimeters  in  diameter  and  placed  ten  milli- 
meters   apart. 

On  one  side,  over  each  of  these  perforations 
is  placed  pieces  of  platinum  of  thicknesses 
varying  from  0.005,  0.01,  0.02,  0.04,  0.08,  0.16, 
0.32,  and  0.64  (in  geometric  progression).  The 
lead  plate  is  enclosed  in  wood.     A  small  bar- 


ium   platino-cyanide    screen,    framed    in    lead 
glass  is  placed  on  the  other  side.     (Fig.  138.) 

For  the  determination  of  the  penetration  of 
a  particular  ray,  the  lead  disc  is  held  towards 
the  tube  and  the  fluorescence  of  the  rounded 
areas  on  the  screen  noted.  The  greater  the 
penetrability  of  the  ray,  the  greater  the  num- 
ber of  fluorescent  spots. 

Thus,  if  six  fields  of  the  scale  are  illumin- 
ated, the  tube  is  described  as  having  a  ray 
which  is  6  W. 

The  thickness  of  the  layers  of  platinum  used 
in  the  scale  is  such  that  1  W  is  a  ray  with 
which  the  soft  tissues  but  not  the  bones  of 
the  hand  on  the  screen  are  visible,  while  8  W 
is  too  hard  for  outlining  even  the  thickest  part 
of  the  trunk.  This  meter  is  faulty  in  that  the 
distance  and  intensity  of  the  radiation  play 
complicating  parts  in  the  illumination  of  the 
fields,  it  being  not  always  possible  to  tell 
whether  the  quality  of  the  ray  or  the  time 
of  exposure  was  responsible  for  the  illumina- 
tion. 

(c)  Measurement  by  Half  Absorption. 
The  determination  of  the  percentage  of  the 
ray  absorbed  by  a  certain  thickness  of  absorb- 
ing media  may  serve  as  a  coefficient  of  absorp- 
tion. 

.Christen  Meter 

A  meter  has  been  constructed  on  the  basis 
of  the  absorption  of  the  ray  by  varying  thick- 
nesses of  water.  This  method  was  first  sug- 
gested by  Christen.  The  measurement  of  the 
quality  of  the  x-rays,  is  based  on  the  number 
of  cubic  centimeters  of  water  which  will  ab- 
sorb fifty  per  cent  of  the  ray  and  allow  fifty 
per  cent  to  pass  through. 

The  softer  the  ray  the  thinner  will  this 
layer  be.  The  harder  the  ray  the  thicker 
must  be  the  layer  of  water  before  fiftv 
per  cent  of  it  is  lost  by  absorption.  Dis- 
tilled water  was  chosen  because  its  absorp- 
tive index  is  similar  to  that  of  the  human  soft 
tissues,  which  consist  in  great  part  of  water. 
For  practical  reasons  bakelite,  which  is  a 
synthetic  resin  having  the  same  absorptive 
power  as  water  is  used  in  the  construction  of 
the  measuring  instrument. 


98 


CHRISTEN  METER 


It  is  necessary,  therefore,  to  determine  the 
thickness  of  a  layer  of  bakehte  which  will 
absorb  just  one-half  of  the  rays  and  allow 
one-half  to  pass.  The  thickness  is  measured 
in  millimeters  or  centimeters.  The  standard 
which  must  give  a  50%  absorption  is  made  as 
follows : 


Millimeter 
Aluminum 


— P- 


— 4- 


Benoist 


2- 


Benoist-Walter 
6 


4- 


— 3 


Fig.    139. — Graphic    representation    of    the    relation- 
ship between  Benoist  and  Benoist-Walter  scales. 


perforated  lead  plate  is  placed  in  an  opening 
in  a  sheet  of  lead,  adjoining  a  small  window. 
Over  this  window  there  moves  a  stegped 
wedge  of  bakelite  (Fig. 140).  A  fluorescent 
screen  is  placed  so  as  to  cover  both  window 
and  perforated  plate.  The  perforated  plate  is 
at  such  a  distance  from  the  screen  that  the 
circles  of  fluorescence  merge  and  the  screen  is 
evenly  illuminated,  by  a  ray  which  has  been 
half  absorbed.  The  illumination  of  this  part 
of  the  screen  is  compared  to  that  over  which 
the  bakelite  is  placed  and  the  wedge  is  moved 
until  the  areas  are  equally  illuminated. 


a 

3 

P 

f 

>§ 

U. 

>B 

w 

3fe 

>£ 

J3 

11 

CO 

•32? 
fficT? 

0 
C 

P3 

0^ 

S 

S 

-12-! 

-2.0- 
-1.,- 

-2.0- 

-1.8- 

-  9- 

-2.0- 

-l.s- 

-  8- 

-11- 

-1.6- 

-  8- 

-1.6- 

-  8- 

-1.6- 

-  7- 

-10- 

-1.4- 

-1.4- 

-  7- 

-  6- 

-1.4- 

-  9- 

-  6- 

-1.2- 

-  7- 

-1.2- 

-  6- 

-1.2- 

-  8- 

-  5- 

-1.0- 

-  6- 

-1.0- 

-  5- 

-  4- 

-1.0- 

-  b 

-  /— 

-0.,- 

-0.8- 

-0.,- 

-  11- 

-  5- 

-  4- 

-  5- 

-  4- 

-O.e- 

-0.6- 

-  3- 

-0-6- 

-  3- 

—    H~ 

-  4- 

-  3- 

-0.4- 

-0.4- 

-  2- 

-0.4- 

-  2- 

-  2- 

-  2- 

-  3- 

-0.2- 

-0.2- 

-  1- 

-  1- 

-0.2- 

-  1- 

Table  VII 

Comparative  values  of  the  various  scales  for  measur- 
ing ray  quahty.     (Christen.) 


A  plate  of  lead  1x1  cm.  is  so  perforated  by  The  relative  thickness  of  the  bakelite  neces- 

holes  that  the  area  of  all  the  holes  is  equal      sary  to  do  this  is  read  in  centimeters  and  the 
to  the  area  of  the  lead,  between  them.     This      particular  ray  is  designated.  As  first  described, 


SEMI-REDUCING  METER 


99 


the  instrument  was  a  fluoroscopic  one  and  in 
order  to  obtain  an  accurate  result,  it  was  abso- 
lutely essential  to  hold  the  instrument  so  that 
the  fields  to  be  compared  had  the  lar.s^est 
possible  width  and  no  bright  or  dark  zones 
appeared  around  the  border  of  these  fields. 
Only  then  are  the  rays  parallel  to  the  holes 
in  the  half  value  plate. 

Tables  VII  and  \TII  of  Christen  give  the 
comparative  values  of  the  various  meters. 


U 

1 

a. 

be 

C 

o 

c 

lU 

n 

is 

n 

0.2 

1.7 

1. 

1.1 

1-4 

is}    Soft 

0.4 

3.2 

3. 

4. 

3 

2.2 

,3-6 

0.6 

4.8 

4. 

5. 

3 

3.2 

5-10 

4     1 

0.8 

6.2 

4. 

5. 

4 

4.1 

6-12 

5     j-medium 

1.0 

7.5 

5. 

6. 

5 

5.0 

7-15 

6     J 

1.2 

8.8 

6. 

7. 

5 

5  8 

8-18 

6.8 

1.4 

9.8 

7. 

8. 

6 

6.5 

12-2,'^ 

7.10 

1.6 

10.6 

8. 

8. 

7.1 

l-hard 

1.8 

11  3 

8. 

7.5 

2. 

11.9 

9. 

7.9 

Table  VIII 

Comparative    values   of   various    penetrometer   units 
(after    Christen). 

An  instrument  has  been  constructed  by  the 
author  which  may  be  used  radiographically. 


\..^^. 


Fig.   140. — Diagrammatic  representation  of  the  prin- 
ciples  of   Christen   penetrometer. 

B  =  the  perforated  lead  plate 
C  =  the  stepped  wedge  of  bakelite 
D  =  Fluorescent   screen 
F  =  Scale 
G  =  Inde.x. 

The  illumination  of  the  screen  behind  the  per- 
forated lead  plate  is  compared  to  that  behind  the 
bakelite   step. 


A  set  of  bakelite  steps  (  l-"ig.  14,? )  is  arranged 
in  a  circle  around  a  movable  disc  which  is 
provided  with  sixteen  wings  separated  by 
sixreen  spaces  of  uniform  size.  When  this 
disc  is  rotated  by  means  of  clockwork,  only 
one-half  of  the  rays  afi'ects  the  photographic 
plate  placed  underneath  it.  The  developed 
plate  will  show  a  central  circle,  the  blackening 
of  which  corresponds  to  exactly  one-half  of 
the  incident  ray.  Around  this  central  circle 
are  the  shadows  of  varying  density  cast 
by  the  fifteen  bakelite  steps.  The  dark- 
ening of  the  plate  underneath  these  steps  is 
compared  to  the  central  field  and  the  height 
of  that  step  which  matches  is  equal  to  the 
half  value  measure  sought. 

The  rotating  disc  is  provided  with  a  lock- 
spring  so  that  rotation  may  be  properly 
started. 

Christen  has  also  described  a  similar  in- 
strument and  suggests  that  all  radiometers 
in  order  to  be  considered  reliable,  must  be  re- 
ducible to  the  half-value  system. 

The  degree  of  hardness  is  expressed  in  this 
semi-reducing  system  by  the  numerical  value 
in  centimeters  of  the  bakelite  layer.  Thus  a 
1.5  ray  indicated  that  the  ray  has  that  quality 
of  hardness  that  it  is  half  absorbed  by  1.5 
cm.  of  water  or  bakelite.  2.0  ray  is  one  which 
is  reduced  fifty  per  cent  by  2  centimeter  of 
water  or  bakelite.  Such  a  ray  will  be  reduced 
to  thirty-five  per  cent  at  3  centimeters  depth 
of  tissue,  to  twenty-five  per  cent  at  4  centi- 
meters, eighteen  per  cent  at  5  centimeters, 
twelve  per  cent  at  6  centimeters,  nine  per  cent 
at  7  centimeters,  six  per  cent  at  8  centimeters, 
four  per  cent  at  9  centimeters,  and  to  three  per 
per  cent  of  its  original  intensity  at  10  centi- 
meters. 

The  appended  table  gives  the  percentage 
absorption  at  various  depths  for  rays  of  vari- 
ous hardness  in  semi-reducing  units. 

The  dose  reaching  any  depth  in  the  soft 
tissues  is  proportional  to  the  quotient  of  the 
svu-face  energy  divided  by  the  semi-reducing 
unit.  The  table  below  gives  the  percentage  of 
energy  which  is  absorbed  bv  the  various  depths 


100 


ABSORPTION  ESTIMATION 


in  a  layer  1  mm.  in  thickness  when  the  surface 
is  radiated  by  rays  of  various  hardness. 

The  maximum  absorption  of  a  layer  at  a 
certain  depth  below  the  surface  for  a  given 
surface  dose  will  be  attained  when  the  half- 
value  layer  is  equal  to  .7  of  the  depth  of  the 
particular  layer  of  tissue  it  is  sought  to  aiTect. 
Thus  the  maximum  absorption  of  a  2  cm.  ray 


the  skin,  the  maximum  absorption  would  be 
attained  at  this  depth  if  the  part  were  radiated 
by  a  1.4  cm.  ray. 

The  surface  dose  for  any  particular  ray 
may  be  determined  by  estimating  the  absorp- 
tion in  the  first  one-tenth  of  the  absorbing 
layer  of  tissue.  The  greater  this  percentage, 
the  less  the  value  of  the  half-absorption  layer, 


Absorption  T.^ble 


Semi-reducing  unit 

2  mm. 

4  mm. 

6  mm. 

8  mm. 

1  cm. 

1.2  cim. 

1.4  cm. 

1.6cm. 

1.8  cm. 

2  cm. 

3  cm. 

Tissue  layer      2  mm. 

50 

71 

79 

84 

87 

89 

90 

91 

92 

93 

95 

4  mm. 

25 

50 

63 

71 

76 

80 

82 

84 

85 

87 

91 

6  mm. 

12i 

35 

50 

60 

66 

71 

13 

77 

79 

81 

87 

8  mm. 

6 

25 

40 

50 

58 

65 

68 

71 

73 

76 

83 

1  cm. 

3 

18 

31 

42 

50 

56 

71 

65 

68 

71 

79 

1.5  cm. 

U 

9 

18 

27 

35 

42 

47 

52 

56 

60 

71 

2  cm. 

1 

3 

10 

IS 

25 

31 

36 

42 

46 

50 

63 

3  cm. 

1 

3 

7 

13 

17 

22 

2S 

32 

35 

50 

4  cm. 

1 

0 

8 

10 

14 

17 

22 

25 

40 

5  cm. 

1 

3 

3 

8 

12 

16 

18 

35 

6  cm. 

u 

3i 

3 

/ 

10 

12 

25 

/  cm. 

? 

3 

4 

7 

9 

22 

Scm. 

1 

2 

3 

4 

6 

17* 

9  cm. 

1 

2 

3 

4 

12i 

10  cm. 

1 

2 

3 

10 

Table 

IX 

would  be  at  2.85  cm.  beneath  the  skin.  At  this 
depth  in  proportion  to  the  skin  dose  a  ray 
having  a  half-value  of  2  cm.  would  be  ab- 
sorbed to  a  greater  extent  than  a  harder  or 
softer  ray.  Conversely,  if  it  is  desired  to 
aiTect  a  structure  Iving  two  centimeters  under 


the  softer  the  ray.  The  energy  absorbed  in 
the  first  one-tenth  will  be  double  the  amount 
absorbed  in  the  last  one-tenth  when  the  half 
value  layer  is  equal  to  the  depth  of  this  layer 
beneath  the  stu'face.  If  the  half  absorption 
layer  is  but  7/10  of  the  depth  of  the  tissue, 


T.\BLE  OF  Depth  Do3.\ge 
In  Percentage  to  the  Surface  Energy  per  Millimeter  Layer  Thickness 


Semi-reducing  . 

unit 

2  mm. 

4  mm. 

6  mm. 

8  mm. 

1  cm. 

1. 

2  cm. 

1.4  cm. 

1.6cm. 

1.8  cm. 

2  cm. 

2.5  cm. 

3  cm. 

Tissue  layer 

0  mm. 

350 

170 

110 

86 

69 

57* 

49 

43 

38 

34* 

27 

23 

2  mm. 

175 

121 

87 

72 

60 

51 

44 

39 

35 

32 

26 

22 

4  mm. 

88 

85 

69 

61 

53 

46 

40 

36 

32 

30 

26 

20 

6  mm. 

44 

60 

55 

51 

45 

41 

36 

5i 

30 

28 

23* 

20 

8  mm. 

22 

43 

44 

43 

40 

37 

33 

30  i 

28 

26 

22 

19 

1  cm. 

11 

31 

35 

36 

35 

33 

30 

28 

26 

24* 

21 

18 

1.5  cm. 

2 

15 

20 

23 

25 

24 

23 

18 

2U 

20* 

18 

■  16 

2  cm. 

5 

11 

15 

17 

18 

18 

12 

17* 

17 

16 

14 

3  cm. 

2 

3 

6J 

8^ 

10 

11 

7* 

12 

12 

12 

11* 

4  cm. 

3 

4 

6 

17 

3 

8* 

9 

9 

9 

5  cm. 

2 

3 

4 

0 

6 

6 

7 

7 

6  cm. 

2 

2i 

2 

4 

4 

5 

6 

7  cm. 

2* 

3 

4 

a 

Scm. 

2 

0 

4 

9  cm. 

2 

3 

10  cm. 

2 

Table  X 

ABSORPTION  ESTIMATION 


101 


it  is  desired  to  affect,  the  relation  of  surface 
dose  to  the  dose  in  the  depth  of  the  tissue  will 
be  as  2.7:1.     (Table  XL) 

Thus  if  the  semi-reducing  unit^D  and  one 
side  of  this  receives  radiation.  I,  the  amount 

absorbed  bv  a  laver,  A.  cm.  thick  is  .7  x  I  x      -  • 

D 
Thus  with  a  2  cm.  ray,  the  first  millimeter 
would  absorb  three  and  one-half  per  cent  if 
the  svn^face  radiation  w'ere  one  hundred.  With 
a  1  cm.  ray  the  first  millimeter  would  absorb 
seven  per  cent. 

Christen,  however,  points  out  that  the  study 
of  table  X  would  indicate  that  for  practical 
purposes  it  may  be  considered  that  the  maxi- 
mum absorption  will  be  attained  by  a  ray 
whose  hardness  expressed  in  semi-reducing 
units  is  equal  to  the  depth  of  the  tissue  it 
is  desired  to  affect.  Taking,  for  example,  the 
conditions  given  above  of  a  radiation  having 
the  value  of  1.4  cm.,  we  have  seen  that  its 
maximimi  absorption  would  be  obtained  at 
a  point  two  centimeter  underneath  the  skin, 
if  the  .7  depth  rule  is  strictly  adhered  to.  A 
scrutiny  of  table  X  will  show  that  at  a  depth 
of  2  cm.  beneath  the  surface,  18  per  cent  will 
be  absorbed  while  if  our  more  practical  rule 
is  utilized  and  a  2  cm.  ray  is  used,  the  absorp- 
tion at  a  2  cm.  depth  will  be  17.  The  differ- 
ence is  so  slight  as  to  be  practically  negligible. 

It  is  Christen's  contention  therefore  that  if 
one  desired  to  obtain  as  great  an  amount  of 
energy  at  a  certain  depth  as  possible,  such  a 
ray  should  be  used  whose  semi-reducing  unit 
is  equal  to  the  thickness  of  the  layer,  beneath 
the  surface  it  is  desired  to  affect. 

In  table  XI  Christen  has  determined  the 
percentage  of  energy  reaching  the  upper 
tenth  of  a  layer  of  tissue  (2nd  column) 
and  the  energy  absorption  in  a  layer  of  the 
same  thickness  at  a  depth  equal  to  w  (thick- 
ness of  semi-reducing  luiit )  (column  3),  the 
quotient  of  the  first  to  the  second  giving  the 
relationship  of  the  surface  energy  to  the  deep 
dosage,  therefore  the  absorption  quotient,  as 
shown  in  column  4. 

Figure  141  gives  a  graphic  idea  of  this,  the 


ABSORPTION   QUOTIENTS 


Half  Value      Uppermost 


Layer 
a=l/4  w 
a=l/3  w 
a=l/2  w 
a=-7/10  w 
a^w 

a=10/7  w 
a=2  w 
a=3  w 
a^4  w 


Layer 

242% 

187% 

129% 

94% 

67% 

47% 

34% 

23% 

17% 


Deep  Layer 
15% 
23% 
32% 
35% 
33% 
29% 
26% 
18% 
15% 


Absorptiori 
Quotient 

16.1 
8.1 
4.0 
2.7 
2.0 
1.6 
1.36 
1.28 
1.1 


Tablk  XI 

absorption  curves  being  shown  for  rays  of 
various  penetration.  The  intensity  is  given 
for  all  the  rays,  being  indicated  in  the  left 
upper  portion  of  the  diagram  as  I=Io  (sigri 
for  intensity  of  beam  when  it  enters  the 
tissue).  When  the  radiation  has  passed 
through  its  semi-reducing  layer,  a,  its  intensity 

has  sunk  from  I=I„  to  1=  -^.  It  will  be  noted 

in  the  diagram  that  the   softest  rays  have  a 

w 
semi-reducmg  unit  value  of  a=  —.-.     This  is 

reduced  to  fifty  per  cent  of  its  value  in  the 
first  quarter  of  the  reducing  layer.  The  ver- 
tical line  in  the  upper  left  hand  corner  indi- 
cates how  much  of  the  radiation  is  absorbed 
after  passage  through  the  first  tenth  of  the 
tissue  layer.  The  intensity  of  this  radiation 
at  the  depth  may  be  studied  by  the  altitude 
of  the  triangle  in  the  lower  right  hand  portion 
of  the  diagram.    It  is  to  be  noted  that  the  alti- 

w     w 
tude  increases  for  the  rays  ^  '  ^   and  that  it 

reaches  its  maximum  value  in  the  ray  indi- 
cated 7/lOw  (see  theoretical  rule).  The  dift'er- 
ence,  however,  between  this  and  the  ray  w  is 
very  slight  (see  practical  rule).  From  this 
point  upward  to  the  very  hardest  ray,  w,  the 
altitude  of  the  triangle  decreases,  indicating 
a  diminution  of  the  amount  of  energy  ab- 
sorbed in  the  depth. 


102 


WAVE  LENGTH  MEASUREMENT 


Filtration  bv  aluminum  apparently  raises 
the  half-absorption  layer  value  of  the  ray  as 
shown  in  the  followino-  table : 


Filter 

Half 

Absorption  Layer 

No  filter 

1.5 

.5  mm. 

1.8 

1       mm. 

2 

2       mm. 

2.25 

3       mm. 

2.25 

4       mm. 

2.5 

T 

\BLE   XII 

3.  Bv   Me.\surixg    A\'.\ve    Length    of    the 
Rav 

The  shorter  the  wave  length  of  an  x-ray  the 
greater  its  penetrating  power.  The  higher  the 
voltage  used  to  generate  the  ray,  the  shorter 
the  wave  length,  but  as  the  highest  voltages 
are  used  the  quantity  of  radiations  of  both 
long  and  short  wave  lengths  are  markedh' 
increased. 


The  wave  length  of  a  beam  of  x-rays  is 
measured  by  reflecting  it  through  parallel 
planes  of  atoms  in  a  crystal  of  salt,  and  Iftiow- 
ing  the  distance  separating  the  atoms,  the 
wave  length  can  be  determined. 

The  wave  lengths  have  been  studied  by  Hull 
by  means  of  an  x-ray  spectrometer  construc- 
ted on  the  same  principle  as  the  ordinary  light 
spectrometer.  In  the  latter  instrument  the 
colors  and  their  relative  intensity  in  a  beam 
of  light  reflected  by  means  of  a  prism  are 
studied,  and  a  record  obtained  of  each  color 
(wave  length)  and  its  intensity.  Because  of 
the  short  wave  lengths  of  the  x-rays,  the  prism 
is  replaced  by  a  crystal  of  rock  salt  and  the  in- 
tensity is  measured  by  a  photographic  plate  or 
ionization  chamber  instead  of  a  photometer 
as  with  light. 

The  crystal  of  salt  reflects  each  wave  length 
to  a  different  degree  (angle).  The  ionization 
chamber  is  moved  through  all  angles  of  re- 
flection, from  the  smallest  to  the  largest  and 
the  intensities  of  the  various  reflected  beams 
are  caught  in  the  ionization  chamber  and  the 
intensity  of  each  wave  length  is  estimated. 

By  charting  the  \-\-ave  lengths  horizontally 
(abscissa)  and  the  intensities  vertically  (ordi- 


— 

— 

— 

~1 



"N 

VB 

\ 

s 

•^'Jrs^SSr- 

N 

^ 

\ 

r 

\ 

— 

i>. 

■ 

/ 

\, 

*0 

"/ 

\ 

S 

/ 

\ 

s 

/ 

^ 

j_ 

1 









Fig.    141. 


Fig.  142. — Shows  the  spectrum  obtained  of  a  tung- 
sten target  with  40.000  volts  and  i  milliampere. 
The  scale  of  wave-length  is  laid  of?^  horizontalh' 
and  is  measured  in  the  so-called  Aengstrom  unit, 
which  is  a  hundred-millionth  of  a  centimeter. 
The  intensity  of  each  wave-length  is  equal  to 
the  vertical  distance  from  the  corresponding 
point  on  the  horizontal  axis  up  to  the  curve. 
For  example,  the  intensit5'  of  the  rays  of  length 
.3  is  zero  :  that  is,  no  rays  this  length  are  pro- 
duced by  the  tube  operated  under  the  above 
conditions.  Ra\-s  .35  length  have  an  intensit}-  of 
55  and  the  maximum  intensity  97  is  attained  by 
rays  having  a  wave  length  of  .42  (Hull). 


QUANTITATIVE   MEASUREMENT 


103 


This  measurement  is  destined  to  gain  in  im- 
I)ortance  and  practical  value  as  its  technique  is 
simplified.  It  is  by  virtue  of  its  wave  length 
that  a  particular  ray  has  its  characteristic 
qualities,  physical  and  biological. 

According  to  Bragg  the  wave  length  of  an 
x-ray  is  proportional  to  the  square  of  the 
atomic  weight  of  the  radiating  element. 

j\Ie.-\.surement  of  Quantity 
The  intensity  of  x-ray  at  any  point 
may  be  defined  as  the  energy  falling  on 
1  sq.  cm.  of  surface  passing  through  the 
point.  This  intensitv  diminishes  inversely 
with  the  square  of  the  distance  of  the 
target  from  the  receiving  surface.  In  con- 
sidering the  efifect  of  the  ray  the  duration 
of  the  radiation  becomes  a  factor.  In  con- 
sidering the  dosage  the  absorption  in  various 
depths  of  the  tissue  becomes  a  factor.  If  the 
intensity  reaching  a  certain  area  is  arbitrai'ily 


.  143. —  (Photo.)  Penetrometer  based  on  the 
principles  of  the  Christen  half-valency  method. 
The  meter  consists  of  a  lead  disc  with  si.xteen 
tongue-like  projections.  These  are  of  such  size 
that  they  are  equal  in  area  to  the  sum  of  the 
spaces  between  them.  The  disc  and  its  projections 
are  made  to  revolve  by  means  of  a  clock  ar- 
rangement. Located  at  the  periphery  are  fifteen 
blocks  of  bakelite  of  varying  thickness.  The 
meter  is  placed  on  the  plate  and  by  a  spring 
release  the  lead  disc  is  made  to  revolve.  After 
an  exposure  of  five  seconds  the  plate  is  devel- 
oped and  a  comparison  of  the  photographic  den- 
sity of  the  ring  corresponding  to  the  area  under 
the  revolving  sectors  and  the  densities  under 
the  various  piecesof  bakelite  is  made.    (Hirsch.) 


Stated  as  400  at  a  distance  of  10  inches  from 
the  target,  at  20  inches,  the  energy  would 
be  but  14  or  100,  and  at  thirty  inches  but  one- 
ninth,  or  44  4/9ths.  To  get  the  same  in- 
tensity, therefore,  at  an  increased  distance,  it 
is  necessary  to  increase  the  time  as  the  square 
of  the  distance.  Thus,  if  at  ten  inches,  two 
seconds  were  required  to  get  a  certain  effect,  at 
20  inches,  or  twice  the  distance,  4  x  2  or  8 
seconds  and  at  thirty  inches,  three  times  the 
distance,  9  x  2  or  18  seconds,  would  be  re- 
quired. 


FI7.  144. — Radiograph  of  the  penetroineter.  The  disc 
was  not  revolving.  The  darkened  sectors  under 
the  lead  show  the  effective  absorption.  The 
varying  densities  of  the  15  strips  of  bakelite 
are  shown  in  the  periphery. 

Intensity  may  be  measured  by  the  following 
methods : 

1.  Electrical. 

If  the  voltage  is  kept  constant  the  milliam- 
perage  measures  the  current  passing  in  the 
tube  and  gives  a  rough  estimate  of  the  inten- 
sity of  the  ray.  It  is  inaccurate  and  only  rela- 
tive, because  all  the  cathodal  energv-  is  not 
converted  into  x-rays  and  there  are  other  fac- 
tors, shape  of  current  curve,  frequency  of  in- 
terruptions, etc.,  which  are  to  be  considered  in 
the  current  production. 

2.  By  the  heat  produced  by  complete  ab- 
sorption. 

This,  however,  is  no  practical  index  of  the 


104 


IONIZATION  METER 


actual  energy  of  the  x-ray  for  the  heat  pro- 
duction is  actually  very  small. 

3.  Fluorescence. 

The  fluorescent  effect  of  a  beam  is  compared 
to  the  fluorescence  excited  by  a  standard 
source,  as  radium,  but  the  greater  fluorescent 
power  of  soft  rays  and  the  unevenness  of  the 
fluorescence  of  the  diiTerent  parts  of  the  same 
screen  and,  fatigue,  make  this  method  unreli- 
able. 

4.  Ionizing  action. 

The  total  ionization  is  a  reliable  measure 
of  the  energy. 

An  ionization  meter  has  been  constructed 
which  is  called  the  iontoquantimeter.  It  con- 
sists of  an  ionization  chamber  which  is  placed 
on  the  receiving  surface.  Thoroughly  insu- 
lated leads  extend  to  sensitive  electrometer. 
The  circuit  in  which  the  chamber  is  placed  is 
charged  and  the  needle  of  the  meter  is  adjusted 
in  such  a  wav  that  it  indicates  O.    Bv  ionizing 


Fig.  145. — Radiograph  of  the  penetrometer.  The 
lead  disc  has  been  in  motion  for  five  seconds 
and  the  tube,  backing  up  a  two-inch  gap,  was 
energized  by  five  milliamperes.  The  compari- 
son of  the  densities  of  the  ring  to  the  bakehte 
shadows  shows  that  this  density  corresponds 
to  that  sector  numbered  .6.  This  means  that 
the  rays  from  this  tube  will  be  reduced  to  fifty 
per  cent  at  a  depth  of  .6  centimeters  under  the 
skin,  and  reduced  to  twenty-five  per  cent  at  1.2 
centimeters. 

the  air  in  this  chamber  the  x-ray  diminishes 
the  resistance  of  this  circuit  and  the  intensity 


of  the  ionization  is  indicated  by  the  deviation 
of  the  needle  over  a  scale  which  is  graduated 
in  Kienbock  units.  Various  scales  have  been 
constructed  for  rays  of  various  penetrating 
power. 

The  greater  the  intensity  of  the  x-rays,  the 
stronger  the  ionization,  the  greater  the  flow 
of  electricity  in  one  unit  of  time  through  the 
meter  circuit.  The  iontoquantimeter  measures 
the  product  of  intensity  and  radiation  time,  in 
other  words,  surface  energy. 

This  is  independent  of  the  degree  of  pene- 


FiG.  146. — A  test  similarly  made  with  five  milliam- 
peres in  a  tube  backing  up  three  inches  of  gap. 
Note  that  under  these  conditions,  an  .8  ray  was 
used.  This  indicates  that  50%  of  the  ray  will 
be  absorbed  at  the  depth  of  .8  centimeter. 

trability  of  the  ray  or  its  hardness.  The  con- 
sideration of  penetration  is  necessary  in  the  es- 
timation of  dosage.  But  the  meter  permits  the 
comparison  of  the  surface  energy  of  rays  of 
varying  penetration. 

There  are  sources  of  error  which  arise  from 
the  tendency  of  the  ionized  gas  to  regain  its 
non-conducting  state,  because  of  reunion 
of  the  disrupted  parts  (the  electron  and  the 
positive  remainder)  of  the  atom.  To  prevent 
this,  the  ions  must  be  removed  at  high  speed 
by  a  voltage  large  enough  to  secure  saturating 
current.  Though  theoretically  it  appears  im- 
possible to  obtain  a  complete  absorption  by 
the  gas  in  the  chambers  of  all  the  x-rays  enter- 
ing  it,   the   method   of    measurement  still  has 


PHOTOGRAPHIC  METHODS 


105 


practical  value  if  but  a  constant  fraction  of 
the  total  is  absorbed.  The  readings  on  the 
electrometer  must  be  compensated  for  by  a 
consideration  of  the  ionization  effect  of  the 
secondary  rays  characteristic  of  the  gas  and 
those  arising  from  the  walls  of  the  metal 
chamber  struck  by  the  rays. 

The  following  methods  are  utilized  for  the 
estimation  of  x-ray  quantity  in  medicine : 

5.  Photographic. 

The  sensitive  emulsion  of  a  photographic 
plate  is  more  responsive  to  soft  than  to  hard 
rays.  The  effects  are  also  considerably  in- 
creased if  the  particular  ray  is  capable  of 
generating  the  characteristic  rays  of  silver  and 
bromine  and  thus  the  action  on  the  emulsion 
is  really  not  proportional  to  the  actual  ab- 
sorption. But  as  a  comparative  measurement 
this  photographic  action  is  of  value  bearing  in 
mind  certain  limitations.  Areas  of  equal  den- 
sity on  the  same  plate  indicate  that  equal 
amounts   of   energy   were   absorbed   by   these 


Fig.  147. — A  test  similarly  made  with  five  milliam- 
peres,  and  a  tube  backing  up  four-inch  gap. 
One  centimeter  ray  was  thus  obtained.  This 
was  absorbed  50%  at  the  depth  of  I  cm.  and 
reduced  to  25%  at  2  cm.,  i2j/2%  at  3  cm.. 
6.25%  at  4  cm.,  3.125%  at  5  cm. 

areas  but  this  gives  no  idea  of  the  total  energy 
of  the  beam  as  it  emerged  from  the  tube. 

Quantity  may  be  translated  into  electrical 
terms  and  measured  by  photographic  effects. 
Thus  the  quantity  of  radiation  reaching  a  cer- 


tain reacting  surface  may  be  said  to  be  equal  tO' 
the  quotient  of  the  product  of  current,  voltage 
squared  and  time  divided  by  distance  squared,, 
or 

I  \-  t 
D= 
the  quotient  being  in  arbitrary  units.  As 
long  as  the  same  quotient  results  from  the 
varying  of  the  factors,  the  darkening  of  the 
jjlate  will  be  the  same  if  no  object  is  inter- 
posed, but  if  the  latter  condition  exists,  the 
higher  voltage  factor  in  one  formula  will  be 
responsible  for  a  greater  blackening  of  the 
plate. 

By  the  use  of  this  formula  the  effects  of 
varying  the  several  factors  may  be  deter- 
mined.    For  instance, 

1.  Doubling  the  current  (milliamperage) 
doubles  the  intensity. 

2.  Doubling  the  voltage  increases  the  in- 
tensity  four  times. 

3.  Reducing  the  distance  by  half  increases 
the  intensity  four  times. 

4.  Doubling  the  time,  doubles  the  intensity. 
Thus,  by  means  of  the  above  formula,  the 

comparison  of  technique  in  terms  of  quantity 
may  be  made.  The  response  of  the  pastille 
and  the  silver  eniulsion  is  not  the  same.  It  has 
been  found  that  doubling  the  voltage  results 
in  a  doubling  of  a  Holzknecht  pastille  reaction, 
but  in  a  C|tiadrupling  of  the  photographic  effect. 

Kiciibock   iiictliod. 

Strips  of  bromide  of  silver  paper  are  ex- 
posed to  the  x-ray  and  developed  in  given 
metol-hydro  developer  at  18  degrees  C.  for  one 
minute.  The  degree  of  blackening  is  compared 
to  a  standard  scale.  The  scale  is  graded  in  di- 
visions of  Ix  and  extend  to  lOx 

Errors  in  time  and  temperature  of  develop- 
ment, make  results  unreliable.  Thus  the  same 
strips,  which  at  18  degrees  will  give  a  reading: 
of  5x  will  at  12  degrees  C  give  3x,  at  14  de- 
grees, 4x,  at  27  degrees,  lOx.  There  is  also, 
difficulty  in  differentiating  the  higher  grada- 
tions from  each  other.  The  inability  of  the 
eye  to  detect  small  differences  in  intensity  as 
shown  by  blackening  of  the  photographic  plate 
or  paper  must  always  be  borne  in  mind. 


106 


CHEMICAL  METHODS 


6.   Chemical. 

a)  Chemical  reaction  in  solution. 

1.  Under  the  ray  the  iodine  in  a  solution  of 
iodoform  in  chloroform  is  liberated  in  quanti- 
ties depending  on  the  intensity  of  the  ray. 
A  two  per  cent  solution  of  iodoform  is  utilized. 
When  the  iodine  is  liberated  it  colors  the 
chloroform  and  the  intensity  of  the  color  is 
measured  by  a   standard    (Freund). 

2.  Similarly,  the  x-ray  will  precipitate  calo- 
mel from  a  mixture  of  mercuric  chloride  in 
ammonium  oxalate.  By  a  comparison  of  the 
thickness  of  the  precipitate  with  a  standard 
precipitate,  the  dose  can  be  estimated 
(Schwarz). 

b)  Color  reactions  due  to  dehydration. 
The  x-rays  have  the  property  of  changing 

the  color  of  many  salts.  This  property  is 
utilized  for  the  construction  of  chromoradio- 
meters. 

Several  varieties  of  this  form  of  measuring 
device  exist  in  which  the  various  changes  in 
color  in  strips  of  platino-barium  cyanide,  de- 


The  change  in  color  under  the  action  of 
the  ray  is  from  an  apple  green  to  a  reddish 
brown  and  this  discoloration  also  takes'^ lace 
when  the  pastilles  are  exposed  to  strong  light 


Fig.   148. — The  Tintometer. 

or  to  heat.  Discoloration  also  takes  place  due 
to  lack  of  moisture.  Daylight  restores  the 
green  color  after  exposure.  The  tints  should 
be  compared  by  artificial  light  of  an  incandes- 


ScALES  OF  Quantity. 


Holzknecht 

•    Sabouraud- 

Bordier- 

Kienbock 

Schwartz 

Chromo- 

Noire 

Chromo- 

Photographic 

Precipitation 

Radiometer 

Radiometer 

Radiometer 

Quantitometer 

Radiometer 

Units  H 

Tint 

Tints 

Units  X 

Kaloms 

1   H 

2  X 

1-5  H 

3  X 

i  iv 

3  H 

Tint  0 

6  X 

2  K 

4  H 

Tint  0  to  I 

8  X 

5  H 

Tint   B 

Tint  I 

]0  X 

3  5  k 

6  H 

Tint  I  to  n 

12  X 

7  to  8  H 

Tint  n 

14  to  16  X 

14  H 

Tint  HI 

28  X 

20  to  22  H 

Tint  IV 

40  to  44  X 

Table  XIII 


pending  on  the  intensity  of  the  radiation,  may 
be  read  on  a  graduated  color  scale,  Sabour- 
aud  (2  tints),  Bordiers  (5  tints),  Holzknecht 
(10  tints).  Hampsons  (24  tints). 

The  scales  are  calibrated  on  the  basis  of 
the  energy  necessary  to  cause  certain  biological 
skin  effects.  These  meters  all  have  the  follow- 
ing: characteristics : 


cent  carbon  lamp,  immediately  after  exposure. 
Because  these  pastilles  are  not  very  sensitive 
they  are  often  placed  midway  between  the 
target  and  the  object  irradiated  so  that  the 
pastille  receives  four  times  the  exposure  of 
the  object.  The  scales  are  calibrated  for  rays 
of  medium  penetration,  excepting  the  Sabour- 
aud  and  Xoire  scale  which  is  calibrated  for 


CHROMORADIOMETERS 


107 


hard  rays  and  it  is  therefore  important  in 
translating  scales  to  bear  this  in  mind.  The 
calibrations  are  made  for  unfiltered  rays. 

Sabi)iiraiid  and  Noire 

The  standard  is  a  colored  tablet  called  tint 
B.  The  pastilles  supplied  in  a  booklet  with  the 
particular  standard  which  have  tint  A  are 
exposed  to  the  ray,  until  the  color  matches 
that  of  the  standard  tint  B.  This  quantity  of 
radiation  will  cause  epilation  without  erythema 
of  the  skin. 

Because  of  the  difficulty  in  detecting  slight 
color  changes  in  the  pastilles  and  to  minimize 
the  personal  equation  in  the  determinination  of 
the  various  differences  in  color,  for  the  eye 
of  individuals  differ  in  their  ability  to  recog- 
nize modifications  of  color,  the  Lovibond-Cor- 
bett  tinto-meter  is  of  great  utility,  as  providing 
an  accurate  method  of  estimating  the  degree 
of  coloration  of  the  Sabouraud  pastille. 

The  principle  of  the  construction  of  this 
instrument  is  the  utilization  of  three  series 
of  glass  transparencies,  dyed  red,  blue  and 
green  used  universally  as  standards  for  the 
testing  of  colors.  These  pieces  of  colored 
glass  can  in  a  suitable  viewing  box  against 
a  white  background  be  so  combined  as  to  give 
by  transmitted  light  the  same  tint  as  is  given 
by  the  substance  to  be  studied  which  is 
viewed  by  reflected   light. 

After  many  tests  a  B  tint  of  the  Sabouraud- 
Noire  was  adopted  as  the  standard  tint  which 
would  always  produce  epilation  with  but 
transient  erythema  at  the  16th  to  18th  day 
in  a  case  of  tenia. 

The  color  of  this  tint  B  was  matched 
by  combining  the  green,  blue  and  red  glasses 
in  the  instrument  and  thus  a  standard  obtained. 
Pastilles  exposed  to  the  x-ray  are  now  tested 
against  the  Sabouraud  tint. 

Corbett  modified  this  Lovibond  tintometer. 
The  standards  are  tinted  glasses  colored  for 
fractional  doses  from  ^  B  to  2  B.  These  are 
constant  and  invariable  and  permanent.  The 
apparatus  consists  of  a  viewing  box  provided 
at  one  end  with  an  eyepiece  and  at  the  other 
perforated  with  two  small  holes.     At  the  distal 


end  of  the  box  are  frames  provided  for  the 
insertion  of  the  glass  standards,  that  on  the 
right  for  the  matching  tints,  and  that  on  the 
left  for  the  neutral  tints  if  required.  An  ex- 
tension from  the  back  of  the  instrument  carries 
the  support  for  the  background  which  is  made 
of  standard  white  paper. 

In  the  metal  support  of  the  background 
and  in  the  extension,  holes  are  cut,  through 
which  the  pastille  holder  can  be  passed. 

The  light  to  be  used  is  a  diffused  white  light 
or  an  8  candle  power  carbon  filament  lamp 
with  frosted  glass  and  a  suitable  black  shade 
so  arranged  that  the  background  is  eight  in- 
ches from  the  lamp. 

To  make  the  comparison  a  standard  B  tint 
or  whatever  dose  required  is  placed  in  the 
right  hand  frame  and  the  exposed  pastille  in 
the  left  and  these  are  compared  by  looking 
down  the  eye  piece,  the  color  of  the  pastille 
being  viewed  by  reflected  light,  the  standard 
tinted  glass  by  light  transmitted  from  white 
background.  A  neutral  tinted  standard  is 
placed  in  the  left  hand  frame  between  the  eye 
and  pastille  for  studying  the  efl:ects  of  small 
doses  so  as  to  increase  the  accuracy  of  reading 
when  daylight  is  used. 

Bordier. 

In  this  form  of  measuring  device,  five  stand- 
ard tints  are  provided.  To  make  the  compari- 
son easier,  the  pastilles  are  square  and  are  in- 
serted into  a  rectangular  opening  in  the  stand- 
ard tints. 

HohkuccJit  radiometer  (Fig.  149) 

The  index  is  a  tinted  celluloid  band.  The 
reaction  pastilles  are  a  platino-barium  cya- 
nide compound  5  millimeters  in  diameter.  The 
estimation  is  made  by  placing  an  unexposed 
half  pastille  under  the  colored  celluloid  band  in 
juxtaposition  to  the  half  pastille  which  has 
been  exposed  to  the  x-ray.  Both  these  half 
pastilles  are  moved  up  and  down  until  the  half 
discolored  by  exposure  matches  the  tint  of  the 
imexposed  half  moving  under  the  colored  cel- 
luloid. The  instrument  is  calibrated  for  four 
varieties  of  pastilles. 


108 


HAMPSON'S  METHOD 


Fig.  149. — Holzknecht  radiometer.  C.  Sc.  reddish 
brown  color  band,  under  which  a  semi-circular 
piece  of  screen,  carried  on  Sk.  St.  is  placed. 
The  exposed  pastille  is  carried  on  R.  St.,  moves 
on  Schl.  but  under  a  clear  piece  of  celluloid. 
Schl.  is  moved  until  both  semi-circles  form 
a  circle  of  the  same  color.  Then  the  scale 
which  is  indicated  automatically  is  read  in  the 
notch  of  the  R.  St.  The  other  scales  are 
for  pastille  pieces  which  have  a  slightly  different 
initial  tint. 


of  Sabouraud  and  Noire  radiometer.  The  H 
units  are  accurate  only  when  a  medium  ray  is 
employed.  The  biological  effects  of-  tint 
B,  (S  and  N)  are  different  from  5  H  because 
the  S  and  N  scale  is  calibrated  for  harder  rays. 
It  usually  required  about  9  H  of  a  harder  ray 
to  produce  the  same  skin  results  as  are  ob- 
tained with  6  H  and  a  softer  ray. 


Fig.    150. — Hampson   Radiometer. 


Hampson  Radiometer   (Fig.    150) 

This  consists  of  a  graduated  (25  tints) 
colored  scale.  The  colors  have  no  gloss.  These 
colors  are  arranged  in  the  periphery  of  a  piece 
of  cardboard  which  may  be  turned  so  as  to 
bring  each  color  successively  in  the  centre  of 
a  small  window.  The  exposed  pastille  is 
placed  in  this  window  and  is  matched  to  the 
color  on  the  cardboard.  The  sixteenth 
change  is  equivalent  to  the  Sabouraud  tint  B. 

1  H  is  one-third  the  quantity  of  x-ray  which 
will  produce  an  erythema  in  the  skin  of  the 
face  of  an  adult.  1  H  corresponds  to  2  X  of 
Kienbock's  scale  and  5  H  equals  the  tint  "B" 


1  cm.  ray  (Christen)  will  give  an  erythema 
dose  with  1  Sabouraud.  1.5  cm.  ray  (Chris- 
ten) will  give  an  erythema  dose  with  1.2 
Sabouraud.  2  cm.  ray  (Christen)  will  give 
an  erythema  dose  with  1.6  Sabouraud.  2.5 
cm.  ray  (  Christen  )  will  give  an  erythema  dose 
with  2.0  Sabouraud.  It  is  important  to  re- 
member that  all  tlie  methods  described. 
Sabouraud.  Holzknecht,  Hampson,  measure 
surface  energy.  This  is,  in  a  sense,  a  physical 
estimate  of  dosage.  The  reaction  of  the 
human  tissue  to  this  energy  (biological  dose) 
is  really  the  physical  dose  multiplied  by  the 
sensibilitv  coefficient  of  the  tissues. 


PART  II 
THE   APPLICATION  OF  THE  PRINCIPLES 

OF 

ROENTGENOLOGICAL  TECHNIQUE 


PART  II 

THE  APPLICATION  OF  THE  PRINCIPLES  OF  TECHNIQUE. 
METHODS  OF  ROENTGEN  EXAMINATION 

1.  Fluoroscopy —  Roentgenoscopy — Transillumination. 

Examination   by  means   of  the   fluorescent   screen. 

A.  General. 

B.  Special  Fliiorosco/'ic  Methods. 
(i)   Orthofluoroscopy. 

(2)   Stereoscopy. 

2.  Radiography — Roentgenography — Photographic  Method. 

Examination  by  means  of  tlie  photographic   plate. 

A.  General. 

B.  Special  Radiographic  Methods. 
(i)   Stereography.  ^ 

(2)  Teleography. 

(3)  Serial. 

(4)  Polygram. 

(5)  Kimogram. 

C.  Radiography  zmll  be  studied  under  the  follozving  headings: 

1.  The   Preparation   for  the  Examination. 

2.  The  Exposure. 

3.  Development  of  the  Plate. 

4.  The  Examination  of  the  Plate. 

1.  Tlic  Preparation  for  the  E.vaniination. 

A.  The  tube  is  prepared  for  the  exposure. 

(a)  Tube  stand. 

(b)  Table. 

(c)  Tube  connections. 

(d)  Tube   regulation. 

B.  The  method  of  examination  is  decided  upon. 

(a)  Single  plate. 

(b)  Stereography. 

(c)  Teleography. 

(d)  Serial. 

(e)  Polygram. 

(f)  Kimography. 

C.  The  plate  is  prepared. 

(a)  The  photographic  plate. 

(b)  The  intensifying  screen. 

D.  The  part  is  prepared   for  examination. 

(a)  Postures.  Saoittal 

(1)  Centric       i  Vertical  plane        ).  Fromal 

(2)  Excentric  J  Horizontal  plane  j  ohl'r 

(b)  Immobilization.  ^ 

E.  A  standard  arrangement  between   the   plate  and  the  part  is  elt'ected. 
(a)   Standard  positions. 

2.  The  Exposure. 

A.  Ray  quality. 

B.  Ray  quantity. 

C.  Tube-plate   distance. 

D.  Focal  spot. 

E.  Thickness  of  part. 

F.  Sensitiveness  of  plate. 

G.  Timing  of  exposure.' 

3.  The  Development  of  the  Plate. 

A.  Dark  room. 

B.  Development. 

C.  Fixation. 

D.  Drying. 

E.  Intensifying. 

4.  The  Examination   of  the  Plate. 

A.  Simple  illumination. 

B.  Illumination   for  stereoscopy. 


CHAPTER  XII 
FLUOROSCOPY 

Roentgenosco])y.  or  examinalion  by  means 
of  the  fluorescent  screen,  is  one  of  the  impor- 
tant methods  of  Roentgen  diagnosis.  Because 
of  the  simplicity  and  directness  of  the  fluoro- 
scopic method,  it  has  become  an  essential  part 
of  the  equipment  for  diagnostic  work  accord- 
ing to  the  most  modern  standards. 

The  requisites  of  safe  and  successful  fluoro- 
scopy are:  1.  A  ray  of  proper  quantity  and 
quality ;  2.  A  screen  of  proper  quality,  size  and 
suspension  ;  3.  Proper  sensitization  of  the  eye  ; 
4.  Protection  from  deleterious  effects.  Careful 
attention  to  the  first  three  requisites  will  con- 
tribute in  a  large  measure  to  the  establishment 
of  the  fourth.  Generally  speaking,  the  fluoro- 
scopic stative  should  be  of  such  construction, 
as  to  permit  the  maximum  mobility  of  tube, 
patient  and  screen.  This  means  independence 
of  screen  movement  from  tube  movement. 

S  to  fives 

There  are  two  general  varieties  of  fluoro- 
scopic statives,  the  horizontal  and  the  vertical. 
The  important  part  of  this  apj)aratus  is  the 
enclosure  for  the  x-ray  tube. 

Tube  Box 

This  should  be  a  box  lined  with  sheet  lead, 

lead  casting  or  very  heavy  leaded  rubber  which 

'should    completely    envelope    the    tube.     The 

absorbing  quality  of  the  covering  should  be 

equivalent  to  at  least  3/32"  lead 

This  container  should  be  more  heavily  cov- 
ered over  that  part  opposite  the  active  hemi- 
sphere. Means  for  cooling  the  tube  should  be 
provided ;  a  fan  is  usually  sufficient.  This  is 
set  into  an  opening  in  the  container.  It  should 
run  noiselessly.  The  opening  of  the  box  for 
the  ray  emission  should  be  at  least  five  bv  five 
inches  and  covered  by  a  sheet  of  aluminum  one 
millimeter  thick    Placed  in  front  of  this  should 

II 


be  an  iris,  a  slit  cliai)hragni.  or  both,  the  slit 
being  of  greater  utility.  The  box  should  be  large 
enough  to  provide  sufficient  room  between 
tube-wall  and  box,  and  should  contain 
clamps  within  for  holding  tube  in  position. 
The  box  is  to  be  suspended  by  counterweights 
and  is  to  be  freely  movable  on  ball  bear- 
ings in  all  directions  by  a  single  handle 
which  should  also  contain  the  handles  for  dia- 
|)hragm  and  be  long  enough  to  keep  the  hand 
of  the  operator  moving  the  tube  completely  out 
of  range  of  the  most  divergent  ray.  In  the 
vertical  stative  the  tube  box  should  be  so 
suspended  as  to  make  it  part  of  a  lead  parti- 
tion which  moves  behind  another  immovable 
lead  partition,  containing  a  large  fibre  window 
against  which  the  patient  rests.  In  this  way  a 
double  lead  partition  with  an  intervening  air 
space  is  provided.  The  distance  between  the 
target  of  the  tube  and  the  patient  should  not 
be  less  than  twelve  inches. 

The  fluoroscopic  apparatus  should  stand 
firmly  and  ledges  or  forward  supports  should 
be  removed  so  that  a  couch  or  chair  may  be 
wheeled  directly  against  the  permeable  fibre 
window.  Means  should  be  provided  for  plac- 
ing a  shelf  or  a  table  in  front  of  the 
permeable  window  in  order  to  permit;  the  ex- 
amination of  the  patient  in  the  lateral  posi- 
tion. All  that  has  been  said  in  reference  to 
the  vertical  fluoroscopic  stative  holds  true  for 
the  horizontal.  It  seems  preferable  in  many 
instances,  on  account  of  giving  greater  com- 
fort to  the  patient,  that  a  canvas  topped  table 
be  used.  Means  should  be  provided  for  keep- 
ing the  canvas  taut.  A  pure  fibre  top  or  one 
made  of  a  mixture  of  fibre  and  bakelite  or  of 
wood  will  serve  the  purpose.  One  side  of 
the  table  should  be  covered  with  leaded  rub- 
ber curtains  and  the  other  by  a  leaded  par- 
tition. A  combination  of  a  horizontal  fluoro- 
scope  or  trochoscope,  or  a  vertical  stative  is 
of  great  value  in  the  localization  of  foreign 
bodies  and  the  direct  setting  of  fractures. 
(Figs.  151,  152). 
131 


114 


FLUOROSCOPIC  SCREEN 


Fluoroscopic  Screen 

The  fluorescent  screen  most  commonly  used 
consists  of  platino-barium  cyanide,  calcium 
tungstate  or  zinc  sulphide.  It  should  furnish 
a  maximum  ilhimination  with  a  minimum 
current  and  should  have  proper  contrast, 
freedom  from  lag,  and  permanence  of  coating. 
It  should  be  placed  in  an  air-proof  mounting 
and  be  covered  with  lead  glass  one-sixth  of 
an  inch  thick.  It  is  an  advantage,  also,  to 
have  an  arrangement  on  the  back  of  the  screen 
whereby  the  plate  holder  may  be  clamped  in 
any  position  for  the  purpose  of  making  an 
exposure    during   fluoroscopy. 

With  the  vertical  scope  the  fluorescent 
screen  is  to  be  suspended  independentlv  bv 
counterweights  and  should  be  of  such  weight 
and  suspension  as  to  hang  closely  and  firmly 
against  the  patient  without  pressure.  It  should 
be  possible  at  option  to  adjust  the  screen 
so  that  it  may  move  together  with  tube  box 
and  to  lock  it  in  a  fixed  position.  In  the 
horizontal  apparatus  the  fluorescent  screen 
should  not  be  too  heavy,  and  should  be  fixed 
on  a  slidable  bar  along  the  table  top,  the  screen 
being  attached  to  the  bar  by  a  ball  and  socket 
joint. 

Means  should  also  be  provided  for  rapid 
tracing  of  the  fluoroscopic  image.  This  may 
be  done  in  two  ways.  It  may  be  made  directly 
on  the  glass  covering  of  the  screen  and  from 
this  transposed  to  paper,  when  the  examina- 
tion is  completed.  Another  method  is  to  affix 
an  arrangement  to  the  screen,  whereby  a  piece 
of  clean  glass  upon  which  the  tracing  is  made 
may  be  slipped  in  front  of  the  lead  glass.  The 
patient's  name  and  other  data  are  written 
thereon  and  this  may  be  filed  in  an  envelope 
as  a  record  or  transposed  to  paper.  Tracing 
paper  may  be  suspended  on  a  roll  at  the  top 
of  the  fluoroscopic  screen,  so  that  a  piece  may 
be  pulled  over  the  screen  and  a  tracing  made. 
The  tracing  of  the  heart  borders  and  the  dia- 
phragmatic domes  should  be  made  during 
normal  breathing  and  also  at  the  end  of  forced 
inspiration  and  expiration,  in  vertical,  hori- 
zontal and  lateral  postures.  Such  records  of 
a  case  give  considerable  information  regarding 


limitation  of  motion,  not  only  in  respiratory 
but  also  in  cardiac  and  pericardial  diseases. 
With  the  vertical  apparatus  a  fourteei^  by 
seventeen  inch  screen  should  be  used  in  all 
instances,  when  possible,  for  even  though  the 
entire    screen    is    rarelv    illuminated    during 


Fig.  151. — A  special  trochoscope  (Johnston  and  Grier) 
having  one  pair  of  legs,  situated  at  the 
middle,  the  end  of  the  top  being  fastened 
to  the  wall.  The  tube  box  moves  on  a 
pair  of  tracks  parallel  with  the  length  of 
the  table.  A  subframe,  whose  length  is  placed 
at  right  angles  to  this  frame,  travels  on  the 
tracks  on  wheels.  The  subframe  in  turn  has 
tracks  on  which  the  tube-box  itself  travels 
crosswise  of  the  table.  The  tube-box  can  be 
brought  out  beyond  the  end  of  the  table.  To 
the  subframe  is  fastened  a  pair  of  uprights, 
which  are  grooved  on  their  opposing  surfaces. 
A  lead-lined  board  slides  up  and  down  in  this 
groove  like  a  window  sash  in  the  frame.  A 
second  tube-box  is  fastened  to  the  back  of  this 
board  and  the  Avhole  thing  is  counterweighted. 
The  second  tube-box  moves  lengthwise  along 
the  table.  When  the  subframe  is  moved,  both 
tubes  move  lengthwise  together.  The  cross- 
wise adjustment  of  the  first  tube  and  the 
up  and  down  motion  of  the  second  tube  are 
independent  of  each  other.  Both  tube-boxes  are 
properly  protected  with  lead  and  the  fluoro- 
scopes  used  are  covered  with  lead  glass.  In 
operation  the  light  is  shifted  from  one  tube  to 
the  other  in  a  moment  by  means  of  a  string 
attached  to  a  high  tension  switch  and  held  in 
the  hand.  A  double  foot  switch  is  used  to  give 
a  weak  or  strong  current  as  needed. 

fluoroscopy,  it  nevertheless  offers  a  certain 
amount  of  protection  to  the  operator.  From 
the  lower  edge  of  the  frame  of  the  screen 
should  be  suspended  an  apron  of  lead  rubber 
at  least  eighteen  inches  long  and  as  wide  as 
the  screen.  Several  cuts  in  this  will  permit 
the  use  of  the  palpation  spoons.  Handles 
sheathed  in  lead  are  attached  to  the  frame  for 
protection   of    the   hands    when   manipulating 


TRACING  OF  FLUOROSCOPIC  LMAGE 


115 


the  screen.  The  old  fluoroscopic  viewing  box 
consisted  of  a  small  screen  attached  to  a  pyra- 
midal hood  of  cardboard,  the  eyes  being  ap- 
plied to  the  smaller  end,  so  that  the  examina- 
tion could  be  made  in  a  lighted  room.  This 
has  come  into  vogue  again  because  of  military 
needs.  Such  a  pyramidal  fluoroscopic  screen  has 
been  described  by  Dessani  (Fig.  153).  It  is  to  be 
fitted  to  the  wearer's  eyes  and  kept  in  position 
by  bands  across  the  head.  By  a  hinged  ar- 
rangement the  fiuoroscooe  mav  be  tilted  back 


Fig.   152. — Side  view  of  trochoscope  with   the  table 
top    removed. 

out  of  the  line  of  vision,  ^^'hen  so  done,  the 
observer  looks  through  a  layer  of  ruby  or 
green  glass,  which  permits  operative  procedure 
without  desensitizing  the  eyes. 

Protection 
Too  great  emphasis  cannot  be  laid  on  the 
problem  of  protection.  The  Roentgen  Ray  is 
an  agent  capable  of  causing  considerable  dam- 
age to  the  organism.  Though  this  appears  to 
be  generally  appreciated,  it  is  nevertheless  sur- 
prising to  note  the  utter  disregard  of  this 
danger  during  fluoroscopy,  particularly  with 
the  use  of  the  Coolidge  tube,  where  many  of 
the  limitations  which  gave  a  certain  margin  of 
safety  when  the  Crookes  tube  was  used,  do  not 


Fig.  153. — Operating  Fluoroscope;  a.  Catch;  b,  Fluo- 
rescent  screen   open ;   c,   Lead  glass. 


Fig.  154. — Fluoroscope  screen  (Charlier)  13-18  cen., 
covered  with  lead  glass.  The  back  is  aluminum 
'  <  mm.  thick.  The  hand  is  protected  by  a  cup- 
shaped  shield.  The  handle  bar  is  so  bent  as  to 
take  the  hand  out  of  the  line  of  the  central  rav. 


116 


PROTECTION  DURING  FLUOROSCOPY 


exist.  Carelessness  in  providing  suitable  pro- 
tective measures  is  bound,  sooner  or  later,  to 
lead  to  disastrous  results.  It  must  not  be  for- 
gotten that  the  late  skin  effects  may,  and 
usually  do,  come  on  from  four  to  seven  years 
after  prolonged  exposure.  Immunit}-  from 
such  effects  for  a  year  or  two  instils  a  false 
sense  of  security.  Eternal  vigilance  is  the 
price  of  an  intact  skin.  Such  additional  pro- 
tecting devices  as  lead  rubber  gloves,  are 
essential  and  ordinary  leather  gloves  should  be 
worn  underneath  the  rubber  gloves.  This  is 
particularly  important  if  fluoroscopy  be  used 
for  operative  work  in  fractures.  Lead  glass 
goggles  and  leaded  aprons  are  useful  in  fur- 
ther increasing  safety  in  fluoroscopy. 

Ray  Quality  and  Quantity 

The  tube,  if  of  the  gas  variety,  should 
be  of  medium  focus  and  "  air  regulated,"  if 
of  the  ( Coolidge )  electron  variety  should 
be  of  sharp  focus.  \Mth  the  electron 
tube  the  transformer  provides  a  simple, 
convenient  and  easily  controllable  method  of 
energization.  With  the  gas  tube  a  coil  and 
mercury  or  mechanical  break  give  the  best 
service.  \\^orking  with  a  gas  tube,  whose 
equivalent  spark  gap  value  is  seven  inches  or 
with  a  Coolidge  tube  of  six  inches  and  using 
three  milliamperes,  with  a  filter  of  one 
millimetre  of  aluminum,  an  exposure  of  twelve 
minutes  is  the  limit  of  safety  at  the  usual 
target  skin  distance  if  a  skin  reaction  is  to  be 
avoided.  \\'ith  the  constant  moving  of  the 
body  of  the  patient,  incidental  to  the  exam- 
ination in  all  directions,  no  part  should,  there- 
fore, ever  receive  a  large  fraction  of  a  skin 
dose.  The  quality  of  the  tube  should  be  such 
that  no  more  than  three  to  four  milliamperes 
are  used  with  a  tube  of  sufficiently  high  vacuum 
to  back  up  from  six  to  six  and  one-half 
inches  in  equivalent  gap.  What  should  be 
sought   for  is   detail  with   sufficient  contrast. 

For  pyeloscopy  from  10-20  milliamperes 
may  be  used  with  a  tube  whose  resistance 
equivalent  is  4  inches  of  air  gap. 


Scjisitisatiou  of  the  E\c 

Sensitization  of  the  e3-e  is  extremely  impor- 
tant. To  this  end  the  illumination  of*"  the 
fluoroscopic  room  should  always  be  indirect, 
dim,  and  of  the  bluish  green  tint,  the  color  of 
the  fluorescence  of  the  screen.  Sensitization 
may  also  be  accomplished  by  tiring  the  eye  for 
its  complementary  color,  red. 

Previous  to  the  examination,  the  room, 
which  should  be  well  ventilated,  and  the  air 
kept  in  motion,  should  be  partially  darkened 
and  all  preparations  for  the  examination  then 
made.  The  observer  should  remain  in  partial 
darkness  for  at  least  ten  minutes  and  in  abso- 
lute darkness  for  five  minutes,  before  the  first 
examination  is  begun.  It  has  been  estimated 
that  the  sensibility  of  the  retina  is  increased 
100  times  after  the  first  10  minutes  in  dark- 
ness. The  visible  light  from  the  tube  itself 
must  be  eliminated.  The  static  glow  of  the 
wires  carrying  the  high  tension  may  be  elim- 
inated by  the  use  of  a  tin  or  iron  piping  or 
heavily  covered  cable. 

Should  it  be  necessary  to  move  in  and  out 
of  the  fluoroscopic  room,  colored  glass  should 
be  worn. 

The  Examination 

The  examiner  should  have  everything  at 
hand,  so  that  there  need  be  no  stumbling  or 
fumblins;  in  the  dark  or  turnintr  on  of  lights. 


Fig.    155. — Modification   of   Holzknecht   Spoon,   with 
Cylinder  to  give  Bucky  eitect.     (Lippman.) 


THE  EXAMINATION 


117 


The  fluoroscopic  switchboard  with  primary 
and  filament  control  should  be  at  the  side  of 
the  operator.  It  should  be  movable  on  casters 
and  of  fireproof  construction.  It  should  con- 
tain connecting  posts  for  foot  switch  and 
should  have  a  pilot  lamp,  painted  dark  green, 
suitably  shaded.  The  rheostat  should  have  a 
zero  button.  A  time  switch  should  be  pro- 
vided. The  foot  switch  should  be  placed  in 
a  convenient  situation  and  permit  the  control 
not  only  of  the  energization  of  the  x-ray  tube, 
but  the  general  lighting  of  the  room.  The 
foot  switch  should  have  a  positive  catch,  re- 
leasable  by  jjressure  with  the  heel,  and  be 
of  such  a  construction  as  to  carry  the  full 
load  of  the  machine,  of  sufficient  weight  to 
insure  permanency  in  position.  A  connection 
for  a  pilot  lamp  should  be  provided  and  so 
arranged  that  when  the  potential  is  otT,  the 
pilot  light  is  on  and  vice  versa. 

The  patient  should  stand  or  be  seated 
on  a  revolvable  stool  directly  against  the 
stative.  Those  who  are  too  ill,  may  be 
examined  directly  on  the  horizontal  scope 
or  on  a  chair  with  a  canvas  back  against 
w'hich  a  vertical  stative  may  be  placed. 
It  is  not  necessary  to  bare  the  body.  A  but- 
tonless  or  bookless  shirt  prevents  irritation  of 
the  skin  of  the  precordium  which  may  mani- 
fest itself  reflexly  as  a  variation  of  heart  action 
— myopathic  heart  reflex.  Besides  this  the 
wearing  of  a  shirt  helps  to  reassure  and  calm 
the  patient,  who  is  usually  frightened  by  the 
circumstances  attending  the  examination  and 
emotional  quiet  is  essential  for  the  proper  ex- 
amination,  particularly   of   heart   cases. 

The  examiner  need  not  necessarily  stand 
directly  in  front  of  the  screen,  for  the  obser- 
vations may  be  just  as  accurately  made  when 
standing  to  one  side  and  thus  out  of  the  direct 
path  of  the  rays.  The  examination  must  be 
thorough  but  rapid.  The  energizing  of  the 
tube  must  be  intermittent.  It  is  a  foolhardy 
and  useless  procedure  to  fluoroscope  a  patient 
over  a  long  period  of  time.  A  glance  and  then 
an  interval  of  orientation  and  thought,  then 
another  period  of  observation,  followed  by  a 
period   of    darkness    for   consideration    as   to 


what  is  observed  and  what  is  to  be  sought 
or  still  to  be  determined.  By  this  method 
the  patient  is  safeguarded  and  ])rolonged 
exposure  is  prevented.  The  examination  in 
the  vertical  position  should  be  followed 
by  one  in  the  horizontal  posture.  It  should 
always  be  borne  in  mind  that  there  exists  an 
idiosyncrasy  on  the  part  of  some  individuals 
to  the  ray.  This  has  been  established  beyond 
a  doubt.  The  dried  out,  emaciated  individual, 
suffering  from  old  nutritional  disorders,  is  to 
be  subjected  to  an  examination  for  a  shorter 
period  of  time  than  the  average  case. 

The  examination  should  be  made  in  a  svs- 
tematic  and  definite  manner,  each  portion  of 
the  body  being  scrutinized  in  a  regular  definite 
sequence.  The  tube  is  placed  over  the  mid- 
dle of  the  part  and  the  diaphragm  opened 
widel)'  so  as  to  obtain  a  general  view.  The 
diaphragm  is  then  narrowed  and  the  part  ex- 
amined for  detail. 

Two  manipulative  procedures  are  utilized 
in  fluoroscopy ;  palpation  and  magnification. 
In  roentgenoscopy  of  the  chest  palpation  is 
not  necessary  but  magnification  is  extremely 
important.  The  withdrawal  of  the  screen  not 
only  adds  contrast  to  the  diaphragmed  image 
but  magnifies  it  and  thus  gives  valuable  in- 
formation.     By  this  procedure,    for  instance. 


Fig.  156. 


118 


ORTHOFLUOROSCOPY 


the  movement  of  the  hikmi  shadow  in  mitral 
disease,  and  even  in  normal  but  very  thin  in- 
dividuals, may  be  made  out.  Shadows  due  to 
calcareous  deposits  may  be  differentiated  from 
shadows  of  large  vessels  seen  in  cross  section, 
etc.  Palpation  may  be  made  with  the  hand 
or  with  the  wooden  spoons.  The  modified 
Buckv  diaphragm  and  compression  cylinder 
renders  great  service,  not  only  as  a  means  of 
compression,  but  for  the  fine  dift'erentiation  of 
structures.  Particularly  in  the  examination 
of  the  abdomen,  fluoroscop}^  without  palpation 
is  but  one-half  of  the  examination.  Palpa- 
tion permits  the  study  of  the  outline  and  dif- 
ferentiation of  actual  defects  due  to  invasions 
of  the  visceral  wall  from  extravisceral  condi- 
tions causing  pressure ;  the  determination  of 
fixity  and  mobility  and  of  areas  resistant  or 
sensitive  to  pressure ;  the  isolation  of  shadows 
and  their  localization  ;  the  stimulation  of  per- 
istalsis ;  the  artificial  blocking  for  the  study 
of  the  lumen  by  overdistention. 

Orthodiascopy  or  Orthofluoroscopy 

This  is  fluoroscopy  with  the  central,  axial 
or  perpendicular  ray  or  ray  bundle.  The 
method  has  its  special  application  in  the  de- 
termination of  the  actual  diameters  of  an 
organ  and  for  the  localization  of  foreign 
bodies. 

The  method  is  based  on  the  axiom  "  The 
nearer  to  the  perpendicular  ray  an  object  lies 
the  sharper  and  truer  its  shadow."  By  con- 
sidering therefore,  the  contours  of  an  organ  as 
consisting  of  points,  shadows  of  these  points 
with  a  perpendicular  ray  are  obtained.  These 
are  connected  and  give  an  outline  of  the  organ. 
Thus  taking  AB  (Fig.  156)  its  shadow 
will  be  represented  by  fine  ab — a  shadow 
whose  diameters  are  larger  than  those  of  the 
object.  But  if  the  shadow  of  point  A  is  ob- 
tained by  a  central  ray  it  will  fall  at  C-on  the 
recordi^ig  surface.  The  perpendicular  ray, 
if  now  placed  over  B,  will  fall  perpendicularly 
under  it  on  the  recording  surface  at  D.  The 
straight  line  CD  ec|uals  the  diameter  of  AB 
and  represents  the  projection  of  this  line  in 
its  real  size.     It   is  necessarv,  therefore,   for 


this  examination,  that  the  ray  bundle  perpen- 
dicular to  the  recording  surface  be  first  deter- 
mined. ** 

Dctcnaiiiaii'on  of  the  Vertical  Rav.  This 
may  be  done  by  many  devices.  Bowen  has 
described  a  convenient  instrument. 


Fig.   157. — Metal  cylinder  of  small  bore  for  obtain- 
ing central  ray.     (Bowen). 

It  may  be  adapted  to  any  standard 
tube  stand  with  cone  attachments,  using  the 
cone  fitting  of  that  particular  stand  as  a  base. 
In  the  diagram  (Fig.  158).  let  (A)  be  such 
cone  base;  (B)  a  brass  or  other  metal  tube 
with  J.^  in.  bore  except  at  the  extreme  upper 
end  where  it  is  reduced  to  5  g  in. ;  a  pointer 
rod  may  be  inserted  in  the  tube  and  by  means 
of  (D)  a  set  screw  held  in  place.  The 
pointer  serves  to  indicate  the  point  which  the 
central  ray  will  strike.  An  attachment  may 
be  substituted  for  the  pointer  rod  with  a  plumb 
line  to  indicate  the  course  of  the  vertical  ray. 

The  vertical  ray,  is  that  ray  proceeding 
from  the  focus  which  is  perpendicular  to  the 
plate  or  screen.  In  fluoroscopy  where  the  tube 
is  in  a  leaded  box  with  a  movable  diaphragm 
the  central  ray  may  be  determined  by  a  con- 
venient device  made  from  a  piece  of  brass 
pipe  2"  or  3"  in  length,  set  in  the  center  of 
a  wood  block  3"  square  and  1"  thick. 

The  under  side  is  cut  away  or  rabbeted  ^  in. 
on  all  sides,  leaving  a  shelf  by  which  the  device 
rests  on  the  shutter  which  is  opened  to  fit  it. 

If  the  focus  is  accurately  centered,  the  tube 
will  cast  a  circular  shadow  on  the  screen, 
otherwise    the    shadow    will    be    oval.     Once 


THE  CENTRAL  OR  VERTICAL  RAY 


119 


centered,  the  tube  should  be  so  marked  that  it 
is  possible  to  place  it  in  the  proper  position 
in  the  stand  at  any  time. 

Various  complicated  apparatus  have  been 
utilized  for  the  orthofluoroscopic  examina- 
tion (Figs.  160,  161).  These  are,  however,  no 
longer  in  general  use.     Accurate  results  may 


TK'n'imihiii!i>mi}hmiiiii),>,im,imih 


Fig.    158. — Tube-centering   device.     (Bowen). 

be  obtained  by  simpler  means.  The  examina- 
tion may  be  made  vertically  or  horizontally. 
In  the  latter  posture  the  body  must  be  perfectly 
horizontal.  In  the  vertical  posture  the  part, 
whether  it  be  chest  or  trunk,  must  be  perfectly 
immobilized. 

^^'ith  a  narrowed  diaphragm,  not  more  than 
one  centimeter  square,  the  contours  of  the 
part  are  traced  so  that  the  outline  bisects  the 
small  square  of  illumination  of  the  screen. 
The  outline  is  then  transposed  to  paper  or 
glass.  The  outline  may  be  traced  on  the  skin 
of  the  patient,  by  using  a  small  screen,  six  by 
eight,  which  in  its  center  contains  a  perfora- 
tion large  enough  to  admit  a  pencil  point.    The 


f^^ 


Fig.  159. — Diagram  of  centering  device  applicable 
to  rectangular  opening  diaphragms.  (Cross  sec- 
tion.) 

screen  is  attached  to  the  handle  of  the  tube 
container  in  such  a  way  that  the  tube  follows 
freely  every  mpvement  of  the  screen.     With 


a  diaphragm  opening  sufficient  to  illuminate 
the  screen,  the  borders  of  the  part  are  marked 
out  by  a  series  of  points  on  the  skin  through 
the  hole  in  the  screen,  when  the  hole,  showing 
as  a  dark  spot,  on  the  illuminated  surface,  falls 
at  the  periphery  of  the  shadow  of  the  part.  In 
both  these  methods  it  is  important  that  the  tube 
be  centered  in  its  container  so  that  with  the 
smallest  workable  diaphragm  opening  the  ver- 
tical ray  is  obtained.  \\'hen  the  perforated 
screen  is  used,  the  screen  must  be  so  adjusted 
that  the  central  ray  passes  through  the  per- 
foration. 

Stereoscopy 

Stereoscopy  is  based  on  the  principles  of 
binocular  vision,  whereby  the  images  seen 
by  each  eye  are  combined  into  one  by  the 
brain,  giving  the  sense  of  depth  or  perspective. 
It  is,  therefore,  necessary  that  two  Roentgen 
images  be  obtained  (the  relation  of  the  tube 
to  the  recording  surface  being  undisturbed) 
by  rays  emanating  from  two  focal  points, 
separated  from  each  other  by  a  distance  cor- 
responding to  that  between  the  pupils  of  the 
eyes,  namely  two  and  one-half  inches  (6.5 
cm.). 

This  examination  is  of  the  utmost  value  in 
resolving  the  composite,  superimposed  shadows 
of  the  structures  and  for  the  determination  of 
their  relationship.     It  is  indispensable  for  the 


ny  / 


"^ 


J3I 


-PO 


SchF= 


Fig.  160. — Orthofluoroscopic  apparatus.  The  central 
ray  from  the  tube  (R)  passes  through  the 
diaphragm  (Bl)  through  a  hole  in  the  screen 
(Z)  into  which  a  pencil  is  inserted  to  mark  on 
the  paper  (P)  the  various  points  of  the  heart 
contour.     (Gocht). 


120 


STEREOSCOPIC  FLUOROSCOPY 


isolation  of  the  various  portions  of  the  in- 
testines, particularly  the  colon.  It  is  of  great 
value  for  the  exact  localization  of  the  lesions 
in  the  lung  and  in  the  dift'erentiation  between 
biliary  calculi  and  other  calcareous  bodies  and 
in  the  localization  of  foreign  bodies  in  the 
tissues. 

For  a  successful  stereoscopic  examination 
there  is  necessary 

1.  The  maintenance  of  the  undisturbed  re- 
lationship between  the  immobilized  part  and 
the  fluoroscopic  screen. 

2.  The  radiations  from  two  focal  points  at 
6.5  cm.  from  each  other. 

3.  The  proper  viewing  of  the  image. 

To  make  this  examination  radiographically 
is  simple,  as  will  be  shown  later  on ;  but  fluoro- 
scopically  it  is  more  difficult. 

A  tube  with  two  targets  or  two  separate 
tubes  are  so  arranged  that  their  focal  points 
are  6.5  cm.  apart.  These  are  so  connected 
to  the  energizing  apparatus  that  the  x-rays 
are  given  off  alternately  from  each  tar- 
get, the  image  thus  falling  on  the  fluor- 
escent screen  is  for  an  instant  from  one  direc- 
tion and  the  next  instant  from  the  other.  The 
observer,  as  in  ordinary  fluoroscopv,  views 
the  screen  in  a  darkened  room,  but  there  is 
placed  before  the  eye  a  rotating  shutter.  This 
rotating  shutter  is  propelled  by  a  small  motor, 
which  revolves  synchronously  with  the  com- 
mutating  device  of  the  interrupterless  trans- 
former.    Fig.  161a. 


Surface 
oj  Screen 


Fig.  i6i. — Orthofluoroscopic  apparatus.  The  central 
ray  passes  through  the  diaphragm  ( Bl)  and 
through  the  hole  in  the  screen  at  (AI).  The 
pointer  (Z)  in  line  with  the  central  ray  marks 
on  the  paper  behind  the  tube,  the  points  in  the 
contour   of   the  heart.     (Gocht). 


Fig.  i6ia. — The  Caldwell  stereofluoroscope  gives  a 
stereoscopic  view  by  alternate  e.xcitation  of  two 
X-ray  tubes  and  by  the  selective  presentation  of 
the  screen  images  to  the  eyes.  Fi  and  F^  in  Fig. 
i6ia  are  the  two  focal  spots  alternateh*  excited. 
B  is  the  body  and  Ei  and  E^  are  the  observer's 
eyes.  The  tubes  are  flashed  in  turn,  Fi  giving 
off  rays  when  F^j  is  inactive  and  vice-versa. 
These  flashes  produce  different  images  on  the 
screen  owing  to  the  difference  in  position  of  the 
tubes.  The  images  are  present  at  alternate 
brief  intervals  and  overlap  on  the  screen.  A 
shutter  is  placed  in  front  of  the  eyes,  so  ar- 
ranged that  during  the  instant  that  Fi  is  ex- 
cited only  El  can  see  the  screen,  and  during  the 
instant  F^  is  excited  E^  can  see  the  screen  and 
Ei  cannot ;  the  shutter,  alternately  permitting 
the  eyes  to  see  the  screen  in  synchronism  with 
the  flashes  of  the  two  tubes.  Thus  each  eye  sees 
only  the  proper  linage  for  stereoscopic  vision. 
The  period  of  lag  of  fluorescence  in  the  crystals 
of  the  screen  is  well  within  the  period  of  persist- 
ence of  an  image  in  the  eye,  so  that  the  observer 
is  conscious  only  of  a  continuous  image  similar 
to  that  produced  by  the  successive  images  of  a 
moving  picture.  Here,  however,  si.xty  images 
appear  to  the  eye  in  each  second,  and  in  the  mo- 
tion picture  only  sixteen.  For  the  successful 
operation  of  this  apparatus  the  shutter  must 
synchronize  absolutely  with  the  illumination 
of  the  screen,  which  is  produced  by  successive 
alternations  of  the  supply  current  to  the  trans- 
former. If  the  machine  is  being  operated  on 
5D-cycle  current,  there  will  be  fifty  impulses 
through  each  tube  every  second  and  the  shutter 
must  run  absolutely  sjmchronous.  The  shutter, 
which  is  quite  similar  to  a  moving  picture  shut- 
ter, has  three  wings  which  serve  to  cut  off  the 
vision  through  the  eye  holes  and  three  open 
segments  which  allow  the  light  to  pass.  The 
driving  of  the  shutter  is  accomplished  by  making 
it  the  rotor  of  a  (salient-pole  type  of  syn- 
chronous )  motor,  the  field  Avinding  surrounding 
it  and  placed  just  beneath  the  face  plate. 

(Middleditch.) 


CHAPTER  XIII 
RADIOGRAPHY 

The  above  fluoroscopic  methods,  though  pos- 
sessing many  advantages,  as  regards  simplicity, 
rapidity  and  cheapness  cannot,  however,  be 
considered  sufficient  for  the  determination  of 
all  the  evidence.  Roentgenography  or  the  ex- 
amination by  means  of  the  photographic  plate 
is  the  primarily  important  method.  Aside 
from  the  inability  of  obtaining  a  view  of  de- 
tailed structure,  the  fleeting  glance  of  the 
screen,  in  which  the  personal  equation  plays 
an  important  part,  is  not  comparable  from 
the  standpoint  of  accuracy  to  the  permanent, 
indelible  photographic  image.  The  greatest 
value  of  the  fluoroscopic  method  lies  in  the 
study  of  movement,  for  the  photographic 
method  gives  but  one  phase  of  the  condition, 
and  no  amount  of  serial  exposures  contributes 
as  much  information  regarding  the  mobility 
of  the  tissues  as  does  a  few  minutes'  fluoro- 
scopic study. 

Radiogr.\phy  or  Roentgexogr.-\phy 

The   Examination   by   Means   of   the  Photo- 
graphic Plate  zcill  be  considered  under 
flic   following   headings: 

1.  Preparations  for  the  examination. 

2.  Making  of  the  exposure. 

3.  Developing  of  the  plate. 

4.  Examination  of  the  plate. 

1.  Prepar.-vtioxs  for  E.x.\mix.\tion 

The    Tube    is    Placed    in     the    Tube    Stand 
The  Tube  Stand 

The  tube  should  be  held  in  a  glass  bowl,  the 
glass  of  which  contains  eighty-five  per  cent 
lead  and  is  transparent. 

The  tube  should  be  kept  in  position  by  two 
fibre  or  bakelite  clamps,  which  do  not  need  to 
be  completely  removed  to  release  the  tube. 

The   horizontal   frame,  carrving  the   shield 


or  bowl,  should  be  easily  and  simply  movable 
in  all  directions  by  a  single  handle. 

Cones  and  cylinders  are  placed  in  position 
by  spring  clamps. 

The  bowl  should  be  capable  of  stereoscopic 
displacement,  both  in  the  vertical  or  horizontal 
direction,  automatically.  It  should  be  revolv- 
able  in  a  horizontal  plane  and  capable  of  being 
lowered  to  within  twelve  inches  from  the  floor. 

It  should  be  perfectly  counterweighted  by 
weights,  moving  within  the  hollow  upright 
pillar  of  the  stand.  The  vertical  column  should 
move  on  a  heavy  tripod,  carrying  ball  bearing 
rollers.  It  should  be  capable  of  being  fixed  to 
the  floor  by  a  simple,  though  effective  foot 
push,  which  should  render  it  immobile. 

Where  there  is  a  limited  amount  of  work, 
or  when  CooHdge  tubes  are  used,  it  is  an 
advantage,  as  making  for  the  diminution  of 
the  possibility  of  its  destruction  to  permit 
the  tube  to  remain  in  the  tube  stand.  The 
position  of  the  tube  in  the  stand  is  variable 
for  different  tubes  and  definite  for  each  tube. 
This  refers  not  only  to  its  position  as  regards 
the  relationship  of  the  focal  point  to  the  center 
of  the  diaphragm  opening,  but  also  as  regards 
the  obliquity.  The  tube  shorild  be  kept 
covered  when  not  in  use  and  the  dust  and 
moisture  removed  before  using.  The  tube 
stand,  containing  the  tube,  should,  during  its 
operation,  be  at  least  six  feet  from  the  trans- 
former. 

When  the  number  of  tubes  required  is  large, 
they  should  be  kept  in  cabinets  in  the  room 
where  the  exposures  are  made,  so  as  to  be 
readily  accessible.  Stich  cabinets  should  have 
sliding  doors,  be  dust  proof  and  provided  with 
holders. 

The    Tube  Stand   is  Placed  N'ear   the    Table 
The  Table 

1.  It  should  not  be  high — three  to  three  and 
one-half  feet. 

2.  It  should  be  capable  of  easy  raising  and 
lowering,  with  the  patient  in  place-. 


11211 


122 


THE  TUBE  STAND  AND  TABLE 


3.  It  should  be  so  constructed  as  to  make 
possible  illumination  from  below  upwards, 
either  in  its  entirety  or  in  part. 

4.  It  should  be  tunnelled  for  stereoscopic 
work. 

5.  The  plate  holder  for  tunnel  work  should 
hold  either  a  plate  in  an  envelope  or  a  screen 
in  a  holder. 

6.  The  top  should  be  capable  of  horizontal 
adjustment  for  use  in  vertical  stereoscopic 
exposures. 

7.  The  entire  table  should  be  freely  mov- 
able, yet  capable  of  fixation  to  the  floor. 


Fig.    162. — ^^'all-folding    table. 

A  combination  of  stand  and  table,  as  one 
piece  of  apparatus,  has  certain  advantages,  as 
regards  the  possibility  of  obtaining  more  cer- 
tain and  firm  compression  and  as  regards 
economy  in  floor  space,  but  the  very  flexibility 


of  the  isolated  units  gives  them  a  great  advan- 
tage. 

A  table  arranged  to  fold  against  tiie  wall 
and  to  work  in  combination  with  a  stereo- 
scopic tube  stand,  is  an  instrument  of  con- 
venience where   space  is  limited    (Fig.   162). 

The  table  top  is  made  of  five  ply  built  up 
veneer,  quartered  oak  outside,  6'  1"  x  24", 
hinged  at  one  end,  so  that  it  can  be  closed  up 
against  the  wall,  the  lower  side  being  equipped 
with  a  special  counterbalanced  frame  to  ac- 
commodate 17  X  17  cassettes;  this  table  is 
equipped  with  folding  legs  arrartged  to  auto- 
matically drop  and  support  the  table  when  it 
is  placed  in  the  horizontal  position  and  to  be 
sufficiently  strong  to  support  the  table  with 
the  patient  lying  thereon. 

The  tube  stand  moves  horizontally  on  two 
steel  bars  l}i"  in  diameter,  65"  long,  the  bars 
being  24^"  apart ;  both  the  horizontal  and  ver- 
tical movements  of  the  stand  should  be 
equipped  with  ball  bearings.  The  tube  car- 
riage is  equipped  with  stereoscopic  shift  and 
automatic  catch  for  holding  compression  cones 
in  position  and  is  counterbalanced. 

The    Tube    is    Connected    to    the    Energizing 
Apparatus 

Connections 

The  wires  connecting  the  transformer  to  the 
tube  may  be  on  spring  reels,  by  which  the 
secondary  current  may  be  carried  directly  to 
the  tube,  or  the  high  tension  current  may  be 
carried  from  the  transformer  to  a  system  of 
trolley  wires,  strung  across  the  room.  On 
these  wires  three  reels  are  suspended  for  con- 
nections to  the  tube.  \\'hen  wiring  for  use 
with  the  gas  tube,  three  wires  are  necessary, 
twelve  to  eighteen  inches  apart.  For  use  with 
the  Coolidge  tube,  the  third  wire  may  be  placed 
several  inches  from  the  wire  to  be  connected 
to  the  negative  end  of  the  tube.  In  the  con- 
struction of  such  a  high  tension  trolley 
system  great  care  must  be  exercised  to 
prevent  grounding  or  leakage.  The 
grounding  may  take  place  through  the 
agency   of   the   metal   accessories,   table,   tube 


HIGH  TENSION  WIRING 


123 


stand,  wall,  or  through  accidental  contact  of 
the  human  bod)'.  \Mien  the  energizing  ap- 
paratus is  a  powerful  transformer,  which 
maintains  its  voltage,  there  is  danger  to  life 
from  such  contact.  The  grounding  of  the 
middle  of  the  secondary  winding  of  the  trans- 
foniKT  as  pointed  out  above  is,  there- 
fore, a  safety  measure,  which  is  to  be  con- 
sidered in  an  installation.  Leakage  is  due 
to  the  high  electro-motive  force  and  frequency 
of  the  current,  which  renders  the  air  partially 


Fig.    163. — Connections    from    transformers   to    high 
tension  trolley  system 


conductive  and  gives  rise  to  a  corona.  The 
leakage  between  bare  wires  will  increase,  if 
the  voltage  or  the  length  of  the  wires  is  in- 
creased. A  reduction  in  the  diameter  of  the 
wires  or  in  the  distance  between  them  will  also 
increase  the  leakage.  This  leakage  may  occur 
into  the  insulating  material,  if  the  latter  is 
not  kept  dry  and  dust-proof,  and  by  gradual 
carbonization,  the  insulating  property  of  the 
material,  wood  or  rubber,  may  be  destroyed. 
Hence,  all  parts  which  carry  the  secondary 
current  should  receive  constant  attention.  The 
high  tension  wiring  must  be  carried  through 
walls  or  partitions  in  large  micanite  tubes 
three  inches  in  diameter,  filled  with  wax.  The 
wires  should  be  attached  or  supported  from 
walls  or  ceiling  by  hard  rubber  rods.  Instead 
of  copper  wire,  rigid  systems  of  gas  pipe, 
which  need  not  be  more  than  half  an  inch 
in  diameter,  are  now  and  then  installed  and 
effectually  prevent  corona.  These  carry  metal 
rings,  from  which  the  reels  are  suspended.  In 
the  Coolidge  system  it  is  important  that  the 
wire  carrying  the  low  tension  current  be  of 


pure  copper,  not  too  fine,  and  as  short  as 
possible.  Corona  losses  are  important  be- 
cause not  only  is  the  x-ray  output  affected,  a 
consideration   in  therapy  where  high  voltage 


!     ,,.    "^      ,     I 

3 

': 

-1 

4^ 

W--^-. —-HI 

c 

/.Sl\ 

Fig.   164. — Four-way  high-tension   switch. 

and  small  currents  are  used,  but  the  corona 
itself  prevents  the  complete  darkening  of  the 
room,  which  is  necessary  in  fluoroscopy. 
The  suspended  wires  from  the  reels  should 
not  hang  less  than  seven  and  one-half  feet 
from  the  ground.  When  the  wiring  is  to  be 
adapted  to  several  units  in  the  same  room,  as 


Fig.  165. — Grounding  the  accessory  anode  of  an  x-ray 
tube  \vhen  high  voltages  are  used   (Wintz). 

to  tube  stands  in  one  part,  fluoroscope  in  an- 
other, a  high  tension  switch  (Fig.  164)  may 
be  mounted  in  the  center  of  the  room  and  the 
current    directed    to    the    desired    apparatus. 


124 


GAS  TUBE  TESTING 


These  switches  are  made  of  bakeHte,  the  con- 
tacts being  between  two  opposing  copper  but- 
tons. 

To  obviate  static  discharges  to  the  tube 
stand  and  patient,  where  high  voltages  are  used 
for  energization,  the  grounding  of  the  tube  by 
connecting  the  accessory  anode  to  earth  makes 
for  quiet  working  of  the  tube  and  prevents 
spark  discharges  to  patient.  It  is  important 
that  the  anode  grounded  be  so  placed  that  the 
grounding  does  not  interfere  with  the  cathodal 
discharge. 

The  Tube  is  Tested 

The  penetrability  of  the  rays  increases  with 
the  increase  of  vacuum.  Though  the  photo- 
graphic and  chemical  effects  depend  on  many 
factors,  nevertheless,  per  se,  the  chemical  effect 
in  relation  to  a  single  layer  of  bromide  of 
silver  of  a  hard  ray  is  less  than  the  effect  with 
a  soft  ray. 

It  is  first  important,  therefore,  to  deter- 
mine the  degree  of  vacuum  of  the  tube.  For 
tubes  of  low  vacuum  only  little  energy  is  re- 
quired ;  those  of  high  vacuum  require  a  cur- 
rent of  corresponding  greater  e.  m.  f.  and 
current  strength.  A  tube  so  evacuated,  that  it 
backs  up  2  and  3  cm.  of  parallel  gap  produces 
x-rays  of  very  feeble  penetration,  barely  able 
to  show  the  bones  differentiated  from  the  soft 
parts  of  a  finger ;  such  a  tube  is  called  "  very 
soft." 

If  the  vacuum  of  such  a  tube  is  increased, 
detailed  structure  of  the  bones  become  visible 
and  can  be  distinctly  dift'erentiated  from  the 
soft  parts  and  the  muscle  planes  can  be  differ- 
entiated from  the  superficial  tissues.  The 
vacuum  of  such  a  tube  is  equivalent  to  a  spark 
length  of  about  six  to  ten  centimeters  and  is 
called  a  soft  tube.  If  the  vacuum  is  still 
higher  the  increase  in  penetration  is  marked, 
so  that  the  bones  cast  only  a  faint  shadow 
and  there  is  scarcely  any  differentiation  be- 
tween the  bones  and  soft  tissues,  yet  such  a 
tube  may  be  exactly  suited  for  the  dehneation 
of  the  structures  of  such  a  dense  portion  of 
the  body  as  the  head  or  lumbar  spine  or  the 
pelvis  of  a  corpulent  individual. 

It   is   thus   apparent   that   a   tube    must   be 


selected  which  has  a  vacuum  equivalent  to  the 
penetration  desired  for  the  particular  ex- 
amination. *■ 

The  methods  by  which  the  vacuum  of  the 
tube  may  be  determined  have  been  outlined. 

Practically  only  three  are  utilized  -in  radi- 
ography : 

1.  Appearance. 

2.  Equivalent  gap. 

3.  ]\Iilliamperemeter. 

1.  The  study  of  the  fluorescence  of  the  tube 
will  indicate,  first,  whether  the  tube  is  cor- 
rectly energized,  as  regards  the  polarity  of 
the  charge,  and,  secondly,  the  state  of  the 
vacuum.  In  a  tube  of  low  vacuum,  there  is 
considerable  bluish  color,  particularly  about 
the  accessory  anode.  There  is  no  sharp  line 
of  demarcation  between  the  active  hemisphere 
and  the  positive  half  of  the  bulb.  In  a  soft 
or  medium  tube,  the  line  of  demarcation  is 
clear.  The  active  half  of  the  tube  is  of  a 
bright  green  fluorescence ;  the  other  half  is 
dark.  As  the  vacuum  increases,  the  active 
hemisphere  loses  its  brilliancy,  becomes  a 
grayish  green,  numerous  flickering  spots  are 
visible  and  the  fluorescence  is  imsteady.  This 
method  is,  of  course,  of  no  utility  in  the 
Coolidge  tube,  which  is  non-fluorescent. 

2.  Between  the  secondary  terminals  of  coil 
there  is  an  arrangement  for  varying  the  dis- 
tance between  them.  This  is  called  a  variable 
spark  gap.  The  ends  of  these  terminals  are 
pointed.  One  pointed  rod  is  movable,  the 
other  stationary.  The  movable  rod  is  con- 
trollable at  a  distance  by  a  spring  and  string 
arrangement  and  a  scale  affixed  permits  the 
reading  in  centimeters  or  inches  of  the  dis- 
tance of  the  separation  of  the  two  points. 
The  resistance  of  the  tube  as  measured  by 
the  parallel  gap  is  an  index  of  the  voltage 
necessarv  to  energize  it,  and  therefore  of  the 
penetration  of  the  emitted  ray. 

3.  The  milliamperemeter  reading  gives  the 
current  value  and  when  studied  in  connection 
with  the  equivalent  gap  gives  the  energy  value 
of  the  tube. 

Is  it  desired  to  energize  a  tube  with  a  volt- 
age equivalent  of  a  three  and  one-half  inch 


GAS  TUBE  REGULATION 


125 


gap,  the  gap  is  set  for  this  distance  and  the 
tube  energized.  If  the  discharge  leaps  across 
the  gap  instead  of  into  the  tube  the  latter 
must  be  reduced.  This  is  accomplished  by  the 
various  regulating  devices  described,  which, 
however,  are  only  practical  when  applicable 
from  a  distance,  that  is  from  behind  the  par- 
tition which  shields  the  operator. 

There  are  several  such  methods. 

1.  A  string  with  a  weight  is  fastened  to  a 
regulating  wire  and  this  is  led  through  loops 
hanging  from  the  ceiling  to  the  operator  behind 
the  protective  screen.  The  wire  is  lowered 
by  releasing  the  cord  (  Fig.  166).  A  variation 
of  this  form  is  one  in  which  the  regulating  wire 
is  kept  by  a  spring,  so  as  to  leave  a  gap  be- 
tween the  end  of  the  wire  and  the  cathode. 


M 


^: 


Fig.  i66. — By  means  of  the  cord,  the  regulating  wire 
A  is  brought  near  the  cathode  end,  and  the  cur- 
rent carried  to  the  regulating  chainber. 


By  drawing  on  a  cord,  the  wire  is  depressed, 
so  as  to  come  in  contact  with  the  cathode,  thus 
allowing  the  current  to  pass  through  the 
regulator. 

The  disadvantage  of  these  methods  is  that 
the   sparking   occurs   near   the   patient. 

2.  As  shown  in  fig.  167,  a  third  wire  ex- 
tends from  the  transformer  or  coil  to  the  regu- 
lating chamber.  The  regulating  spark  gap 
is  at  A,  far  away  from  the  tube  and  patient, 
and  the  metallic  arm  A  is  moved  by  a  string 
which  passes  to  the  operator  within  his  safety 
cabinet  or  behind  his  shield  until  it  touches 
the  negative  terminal  of  the  energizing  appa- 
ratus. 


There  are  two  methods  of  regulating  tubes 
with  osmoregulators  : 

1.  The  palladium  tube  is  heated  liy  a  small 
gas  burner,  the  light  of  which  can  be  regulated 


Fig.  167. — Regulating  the  tube  by  a  third  wire  from 
transformer  to   regulating  chamber. 

from  a  distance,  by  controlling  the  supply  of 
gas. 

2.  A  tiny  spirit-lamp  is  attached  to  the  pa!-' 
ladium  tube,  near  the  cathode  neck.  This 
little  spirit-lamp  may,  from  behind  the  screen^ 
l)y  means  of  an  india-rubber  tube  and  ball  be 
tilted  so  as  to  come  in  contact  with  the  thermo- 
regulator.  The  lamp  lights  itself  from  the 
sparking  of  the  circuit  by  a  very  tiny  gap  at 
the  cathode,  and  heats  the  palladium  tube. 
^^'hen  the  ball  is  released  it  is  tilted  back  again 
bv  a  spring  under  a  metal  hood  which  extin- 
guishes it   (Caldwell). 

The  air  valve  allows  the  frecjuent  re- 
generation of  a  tube  during  use  by  the  ad- 
mission of,  small  quantities  of  atmospheric  air. 
This  regulation  is  possible  from  the  distance 
bv  using  a  long  india-rubber  tube. 

The  vacuum  is  then  reduced  until  there  is 
a  brush  discharge  with  an  occasional  spark 
across  the  three  and  one-half  inch  gap.  The 
vacuum  of  the  tube  in  its  resistance  is  about 
equal  to  three  and  one-half  inches  of  air  gap 
and  at  this  time  such  a  tube  is  called  "  a  three 
and  one-half  inch  tube." 

An  examination  of  the  milliamperemeter 
will  show  certain  readings,  let  us  say,  fifty- 
five  milliamperes.  A  tube  so  energized  may 
be  ideal  (as  will  be  shown  later)  for  the  de- 
lineation   of    a    certain    ])art    of    the    bodv,    if 


126 


MILLIAMPERE  METHOD  OF  TESTING 


energized  for  a  certain  time  at  a  certain  dis- 
tance with  a  certain  recording  medium. 

The  testing  of  the  tube  with  such  a  large 
current,  fifty-five  milliamperes,  is,  however, 
not  practical.     The  vacuum  in  a  gas  tube  is 


^' 


^ 


ing  button,  would  give  a  reading  of  eight  on 
the  first  button  of  the  rheostat ;  a  five  inch 
tube  would  read  seven,  a  six  inch  tubeeivould 
indicate  six  milliamperes  on  the  test  button 
or  number  1.  These  figures  are  only  arbi- 
trary, cited  to  illustrate  the  testing  by  milli- 
ampere  reading  on  a  certain  low  button  ( with 
a  certain  definite  resistance).  It  is  important 
to  note  that  a  tube  energized  by  55  milli- 
amperes at  three  and  one-half  inch  gap  (ob- 
tained on  the  fifteenth  button)  would  not 
give  a  gap  reading  of  three  and  one-half  inches 
on  nine  milliamperes.  The  gap  at  nine  milli- 
amperes is  unimportant.  The  various  volt- 
ages (penetration,  spark  gaps),  and  the  vari- 
ous current  values  necessary  for  the  delinea- 
tion of  various  structures  in  the  body,  both 
in  radiography  and  fluoroscopy,  will  be  dis- 
cussed later. 


Fig.   i68 

characterized  Dy  marked  unstability.  If,  there- 
fore, when  the  tube  has  attained  the  status  of 
fifty-five  nfilliamperes  at  three  and  one-half 
inch  gap,  considerable  though  definite  resist- 
ance is  thrown  into  the  primary  circuit,  the 
milliamperemeter  reading  will  fall.  If  fifty- 
five  milliamperes  at  three  and  one-half  inches 
had  been  obtained  on  the  fifteenth  button  of 
the  rheostat  and  all  of  the  resistance  of  the 
rheostat  available  is  now  thrown  in,  the  mil- 
liamperemeter may  now  read  9.  In  an  arbi- 
trary way  therefore  it  maj'  be  said  that  this 
three  and  one-half  inch  tube  which  on  the 
working  button  15  gives  us  55  milliamperes, 
is  a  9  tube.  If,  therefore,  it  again  beeame 
necessary  to  have  such  a  vacuum  for  the  ex- 
amination, then,  with  the  same  rheostat  re- 
sistance (for  instance  rheostat  button  1),  the 
vacuum  would  be  regulated  until  on  this  but- 
ton the  tube  gave  a  milliampere  reading  of  9. 
On  the  15th  button,  this  tube  would  then  give 
55  milliamperes  at  3 3^  inch  'gap.  This,  of 
course,  holds  true  for  the  particular  rheostat 
and  supply.     (Table  20,  page  205.) 

We  might  thus  similarly  find  that  a   four 
inch  tube  and  fifty  milliamperes  on  the  work- 


^3 


■«?-,•. 


Fig.   169 

Coolidgc   Tube  Regulation 

Here  we  have  to  deal  with  more  stable  con- 
ditions, hence  the  x-ray  output  is  controllable. 
Successful  radiography  demands  the  use  of 
large  currents  at  the  lowest  voltage  required 
to  give  the  necessary  penetration.  The  regula- 
tion of  the  Coolidge  tube  requii-es  the  use 
of  the  equivalent  gap  and  milliamperage. 
If  the  problem  is  to  obtain  55  milliamperes  at 
a  33/2  inch  gap,  for  example,  the  procedure  is 
as  follows : 


COOLIDGE  TUBE  TESTING 


127 


Method.  I 

The  secondary  terminals  of  the  transformer 
are  separated  for  a  distance  of  three  and  one- 
half  inches.  The  two  wires,  one  for  the  low 
tension  current  and  one  for  the  high,  leading 
to  the  negative  end  of  the  tube,  are  firmly  con- 
nected. The  positive  wire  is  hooked  to  the 
positive  end  of  the  Coolidge  tube. 

1.  The  filament  is  heated.  The  degree  of 
heating  is  controlled  by  a  rheostat  and  the 
amount  determined  by  an  ammeter.  Practi- 
cally, it  has  been  found  that  the  limitations 
for  radiographic  and  fluoroscopic  work  lie 
between  four  and  six  amperes.  Let  us  say 
that  the  filament  is  heated  to  a  point  where 
the  ammeter  indicates  4.5  amperes.  The  tube 
is  now  ready  to  be  energized.  Without  heat- 
ing of  the  filament  this  is  not  possible  and 
the  attempt  at  energization  would  lead  to  de- 
struction of  the  tube. 


Fig.   170 

2.  Where  a  sufficient  number  of  variable 
inductances  are  provided,  the  rheostat  is  not 
to  be  utilized  for  Coolidge  tube  work.  The 
full  output  of  the  secondary  with  a  certain 
inductance  is  used.  As  a  measure  of  safety 
in  accidental  grounding,  a  fixed  resistance  in 
such  a  circuit  has  been  suggested.  However, 
a  certain  inductance  is  selected,  for  example 
number  4,  the  primary  switch  closed  and  the 
tube  energized.  If  the  discharge  leaps  across 
the  gap,  the  heating  of   the   filament    is    in- 


creased until  there  is  a  glow  between  the  sec- 
ondary terminals  with  an  occasional  blue  spark 
leaping  between  them.  The  ammeter  reading 
is  now  made.  It  may  be  4.65.  Then,  with 
the   fourth  inductance  at  a  meter  reading  of 


Fig.  171 

4.65  with  the  particular  Coolidge  tube  and 
machine,  a  voltage  equivalent  of  a  3J^  inch 
gap  is  obtained.  Then,  by  varying  the  induc- 
tance or  the  filament  heating  the  condition 
required  (3j^  inch  voltage  and  55  milliam- 
peres)  is  obtained. 

Most  of  the  installations  have  a  voltmeter 
(connected  across  the  primary)  and  calibrated 
in  inches  gap.  If  properly  calibrated  (this 
must  be  determined  by  comparison  with  actual 
measurement  of  the  gap)  this  meter  should 
give  a  reading  of  3^/4  inches. 

The  method  of  adjustment  has  its  disad- 
vantages in  that  a  slight  change  in  the  heating 
current  (as  shown  by  ampere  reading)  re- 
sults in  a  marked  change  in  tube  current  with 
a  corresponding  fall  or  rise  in  effective  volt- 
age (Figs.  168.  169,  170,  171.  172).  unless  an 
auto  transformer  is  used. 

Method  2 

With  a  given  number  of  milliamperes  a 
definite  and  constant  tube  voltage  may  be 
obtained  with  precision,  if  a  similarly  definite 
and  constant  voltage  be  applied  to  the  primary 
of  the  transformer. 


128 


COOLIDGE  TUBE  REGULATION 


Thus,  if  on  the  thirteenth  button  of  the  rheo- 
stat, the  vohage  consumed  by  the  tube,  when 
it  is  passing  55  milhamperes  is  equivalent  to 
a  3)4  inch  gap,  this  gap  will  be  the  same  at 
any  time,  with  the  same  current  on  the  same 


'  r.<' 


The  next  inductance  or  rheostat  button  is  now 
similarly  tested  and  the  milliamperage  obtain- 
able with  the  various  gaps  is  chartered.  oSuch 
a  chart  is  very  helpful  for  instantly  determin- 
ing the  setting  for  a  certain  milliamperage 
gap  value  of  the  particular  machine.  .  Thus, 
if  forty  milhamperes  with  a  gap  value  of  5)^ 
inches  is  required,  the  chart  shows  that  it  is 
obtainable  on  the  19th  button.  This  button 
is  then  selected  and  the  filament  heated  until 
the  milliamperemeter  reads  forty  and  the 
setting  is  readv  for  exposure.  It  becomes  un- 
necessary to  read  filament  current  or  spark 
gap.  In  practice,  the  milliamperage  is  made 
to  slightly  exceed  that  required,  because  of  a 
slight  fall  when  the  tube  is  energized. 


Fig.  172 

Figs.  168-172.— The  above  five  radiographs  were 
made  with  same  tube  and  same  specimen  and 
same  conditions,  except  that  the  filament  cur- 
rent was  increased  i./io  an  ampere  with  each 
exposure.  Note  the  resulting  change  in  penetra- 
tion. 

button  of  the  rheostat.  Thus,  by  placing  the 
primary  rheostat  at  a  certain  point  and  ad- 
justing the  filament  current  until  it  permits 
the  passage  of  a  certain  required  number  of 
milhamperes,  the  voltage  consumed  by  the 
tube  when  it  is  passing  this  milliamperage  will 
always  be  the  same. 

Charts  may  be  constructed  giving  the 
Spark  gaps  obtainable  on  certain  rheostat  or 
inductance  settings  with  various  milliampere- 
age  values  which  are  of  great  practical  utility. 
These  charts  are  made  as  follows:  The 
rheostat  is  set  at  a  certain  point,  for  in- 
stance, 14.  The  spark  gap  is  now  ad- 
justed to  two  inches.  The  filament  is  heated 
to  permit  this  voltage  to  be  consumed  by 
the  tube  and  the  milliamperage  is  read,  and 
charted.  A  similar  test  is  made  on  the  same 
rheostat  button  for  a  three  inch  gap,  four 
inch  gap  and  so  forth,  charting  all  the  avail- 
able current  and  voltage  variations  obtainable 
with  this  inductance. 


£"0        70        80        90 


Fig.  173. — Transformer  chart  (Shearer).  The  chart 
indicates  the  various  currents  and  voltages 
obtainable  from  the  various  points  of  the  rheo- 
stat or  inductances.  Thus  if  35  millamps.  with 
a  gap  of  4"  is  required  the  chart  indicates  that 
this  may  be  obtained  on  the   i8th  button. 

It  is  thus  seen  that  for  the  Coolidge  tech- 
nique there  becomes  necessary  the  following: 

1.  A  variable  graduated  spark  gap. 

2.  A  milliampere  meter. 

3.  An  A.  C.  ammeter. 

4.  A  volt  or  "  spark  meter." 

5.  A  regulator  for  the  filament  current. 
The  variabJc  spark  gap  should  be  calibrated 

in  ]A  inches,  the  scale  being  large,  so  as  to  be 
clearly  visible  at  a  distance.  The  separation 
of  the  points  should  also  be  possible  at  a  dis- 
tance. The  mounting  of  the  scale  in  glass 
across  the  gap  is  objectionable. 

The  MilUampcrc  Meter  should  be  graduated 


COOLIDGE  EQUIPMENT 


129 


from  0  to  20  with  a  shunt  cajjable  of  changing 
the  reading  from  0  to  200. 

The  Aiiiiiictcr  should  have  a  large  dial 
graduated  in  1/50  of  an  ampere,  the  scale 
extending  from  3  to  6  amperes. 


Fig.  174. — Transformer  chart  (Shearer).  The 
various  current  values  are  charted.  Thus  if 
it  is  desired  to  use  20  niilhamps.,  then  the  chart 
permits  the  determination  that  on  the  17th  but- 
ton, it  may  be  obtained  with  a  4J^"  gap,  on  the 
i8th  button  with  a  6.7"  gap. 


The  Volt  or  S/^ark  Meter  should  be  accur- 
ately calibrated,  the  calibration  being  checked 
by  comparison  with  actual  spark  gap  measure- 
ments. 

The  filament  regulator  shottld  be  of  such  a 
capacity  as  will  prevent  undue  heating  during 
periods  of  two  or  three  minutes.  The  heating 
will  cause  the  needle  to  fluctuate  and  increases 
the  time  necessary  to  obtain  any  particular 
reading  on  the  ammeter. 

The  filament  regulator  should  be  composed 
of  a  gross  and  minute  regulator.  It  has  been 
found  that  the  circuit  is  more  satisfactory  if 
the  gross  regulator  permanently  is  placed  at  a 
certain  point  and  then  the  fine  regulation  is 
made  by  th;;  minute  regulator,  the  resistance 
of  which  is  gradually  introduced  in  the  cir- 
cuit, until  the  required  ctirrent  is  determined, 
thus  eliminating  any  irregularities,  which 
might  cause  confusion  and  which  arise  from 
heating  in  the  minute  regulator.  The  object 
should  be  to  keep  a  maximum  amount  of  the 
minute  regulator  in  the  circuit. 

The  regulator  must  be  adjusted  during  pro- 
longed exposures  to   compensate   for   change 


in  the  resistance  of  the  filament  resulting  from 
heating  of  the  target.  There  is,  also,  a  slight 
change  resulting  from  fluctuations  in  the  elec- 
trical resistances,  etc.,  of  the  line  and  trans- 
former. 

The  coils  of  resistance  wire  in  the  minimum 
regulator  should  not  be  closer  than  1/3  inch 
because  disintegration  of  the  wire  or  dust  may 
short  circuit  the  adjacent  turns. 

Owing  to  the  fact  that  the  electrical  re- 
sistance of  the  tungsten  filament,  w'hen  cold, 
is  approximately  1/10  of  its  resistance  when 
incandescent,  it  is  evident  that  a  suitable  re- 
sistance must  always  be  kept  in  the  circuit, 
else  the  sudden  rush  of  current  through  the 
filament  prior  to  its  heating  will  tend  to  throw 
the  needle  of  the  ammeter  out  of  adjustment. 

Since  the  filament  current  is  of  low  ten- 
sion, it  is  necessar)',  in  order  to  avoid  losses, 
that  the  circuit  be  carefully  made.  The  sup- 
ply should  be  unfluctuating  from  a  source  on 
which  no  other  load  exists.  All  connections 
must  be  absolutely  perfect  electrically,  the 
conductors  being  of  copper.  Any  movable 
connection  such  as  a  reel  must  be  reinforced 
by  flexible  connection.  After  any  new"  or 
changed  connection  has  been  made,  a  check- 
ing of  the  instrument  (ammeter)  must  be 
made. 

A  standard  length  of  wire,  preferablv  12 
B.  &  S.,  must  be  in  this  circttit,  and  this  must 
be  decided  upon  at  the  time  of  the  first  in- 
stallation. After  the  exposure  table  has  been 
determined,  all  changes  must  be  made  to  cor- 
respond with  the  original  in  electrical  re- 
sistance. 

A  change  in  the  length  of  a  reel  wire  of 
only  one-half  a  foot  is  sufficient  to  change 
completely  the  set  up.  It  must  be  borne  in 
mind  that  any  break  in  the  filament  circuit  may 
result  in  puncturing  the  tube,  if  the  current 
and  gap  are  sufficiently  high,  as  this  is  identical 
to  running  the  tube  without  the  filament  in 
circuit;  her.ce  the  importance  of  perfect  con- 
nections. 

The  milliamperemeter,  ammeter  and  spark 
gap  scale  should  be  so  mounted  that  all  three 
are  visible  at  a  single  sjlance. 


130 


ADVANTAGES  OF  COOLIDGE  TUBE 


When  the  Coolidge  tube  is  completely  en- 
closed it  is  necessary  to  determine  whether  the 
tube  filament  is  burning  properly.  An  am- 
meter in  circuit  will  show  the  quantity  of 
current  going  through  the  filament ;  but  in 
some  installations  ammeters  are  frequently 
dispensed  with. 

Johnston  has  suggested  the  following  tell- 
tale device :  A  14  volt  carbon  filament  6  can- 
dlepower  lamp  mounted  in  a  small  porcelain 
base  and  bridged  across  the  12-voIt  line  going 
to  the  Coolidge  tube.  The  14-volt  lamp  is, 
therefore,  in  parallel  with  the  12-volt  filament 
in  the  tube.  When  the  current  is  turned  off 
this  little  lamp  is  out,  with  the  current  on  and 
the  Coolidge  tube  filament  burning  properly 
at  a  red  heat  the  little  lamp  merely  glows.  If 
the  Coolidge  filament  does  not  receive  the 
proper  amount  of  current  or  goes  out,  the  little 
"  telltale  "  flashes  up  to  full  candlepower. 

This  brilliant  incandescence  is  a  danger  sig- 
nal and  avoids  subjecting  invisible  Coolidge 
tubes  to  high  potentials  when  the  filament  is 
not  burning.  The  lamp  when  burning  dimly 
is  a  constant  reminder  of  failure  to  turn  the 
12  volt  current  out  of  the  Coolidge  tube.  This 
is  an  important  consideration,  for  the  life  of 
the  tunsfsten  filament  is  limited. 


The  Coolidge  tube  possesses  several  advan- 
tages over  the  gas  tube ; 

1.  That  of  extreme  adaptability,  b^ng 
readily  adjusted  to  produce  rays  of  different 
penetration. 

2.  It  can  be  used  continuously  for  long 
periods  without  fear  of  damage,  and  maintain 
a  constant  condition.  A  current  of  4  ma.  to 
5  ma.  can  be  continuously  passed  through  the 
tube  for  many  hours. 

3.  It  is  an  instrument  of  precision,  in  con- 
tradistinction to  the  gas  tube,  which  is  not. 

4.  It  is  capable  of  taking  very  large  dis- 
charges from  the  secondary  of  the  coil  or 
transformer ;  these  may  be  used  for  instan- 
taneous exposures. 

Other  advantages  are  the  simplicity  of  the 
technique  and  the  accuracy  with  which  results 
can  be  duplicated.  The  main  disadvantage  of 
the  Coolidge  tube  is  the  relatively  large  size, 
as  compared  to  gas  tubes,  of  the  focal  points 
of  the  target.  Working  with  fine  focal  point 
tubes  demands  lengthy  exposures.  Where 
speed  is  necessary  only  a  broad  focal  point 
can  be  used  with  consequent  loss  of  sharpness 
of  the  imase. 


CHAPTER  XIV 
R ADl OCR APH IC  M ETHODS 

Tlie  tube  being  in  readiness  for  the  ex- 
posure, the  method  of  examination  is  then 
determined  upon. 

General  ILvaiitiiiatioii.  By  this  is  meant  ex- 
amination by  a  single  plate,  which  is  the 
preliminary  method  of  examination  in  all 
cases.  It  consists  in  the  making  of  at  least 
two  views  of  the  part,  through  planes  at  right 
angles  to  each  other,  all  the  precautions  for 
the  minimizing  of  distortion  being  observed. 
To  get  the  views  at  right  angles,  the  part  may 
be  turned,  the  tube  plate  relationship  remain- 
ing unchanged,  or,  the  plate  may  be  applied  to 
the  opposite  surface  and  the  position  of  the 
tube  changed. 

The  making  of  two  exposures  (antero-pos- 
terior  and  lateral)  on  the  same  plate,. is  to  be 
recommended  in  all  cases  where  possible, 
using  an  11  x  14  plate  for  two  exposures  of 
the  knee  or  arm  and  a  10x12  plate  for 
elbow  or  ankle  and  an  8  x  10  plate  for  expos- 
ures of  the  wrist  and  smaller  parts.  This 
method  has  numerous  advantages — it  affects 
an  economy  in  plates,  the  cost  of  two  8x10 
being  greater  than  one  11x14;  there  is  a 
saving  of  time  consumed  in  the  changing  of 
plates,  in  developing,  in  filing  space  and  in 
recording.  It  makes  for  simj)licity  in  ex- 
amination, it  being  easier  and  more  con- 
venient to  examine  two  views  on  one  plate 
than  on  two  separate  plates.  There  is  only 
one  theoretical  objection  and  that  is  the  fog- 
ging of  the  plate  by  the  incomplete  covering. 
By  the  use  of  a  one-quarter  inch  lead  plate, 
such  fogging  may  be  prevented. 

The  plate  should  be  backed  by  a  piece  of 
sheet  lead  at  least  ]/>  mm.  in  thickness  which 
is  to  be  fastened  to  a  1  cm.  thick  board.  The 
board  prevents  the  breaking  of  the  plate  by 
pressure  of  the  part.  Its  lead  covering  upon 
which  the  enveloped  plate  is  placed  prevents 
the  fogging  by  the  secondary  radiation  of  the 
wood.  The  secondary  radiations  of  lead  have 
verv  little  ricnetration. 


As  many  as  four  exposures  may  be  made 
on  a  single  plate  without  the  utilization  of  a 
lead  covering,  by  means  of  a  small  cylinder 
or  cone,  if  it  be  pressed  directly  against  the 
part  and  if  the  tube  has  been  properly  encased 
in  a  protective  covering.  In' gastrointestinal 
examinations  a  lead  marker  is  often  placed  on 
the  umbilicus.  Where  many  cases  are  under 
examination  at  the  same  time,  it  is  advisable  to. 
use  a  lead  numeral  of  different  notation  for 
each  case  and  to  keep  this  numeral  in  posi- 
tion throughout  the  examination.  In  making 
teleoroentgenographic  examinations  of  the 
heart  a  marker  is  often  placed  in  the  supraster- 
nal notch  and  one  at  the  ensiform  cartilage. 
In  making  stereoscopic  examinations  for  the 
determination  of  the  course  of  sinuses  or 
fistulas,  the  mouth  of  the  canal  should  always 
be  indicated  by  a  lead  marker  in  addition  ta 
the  injection  of  the  bismuth  paste  for  the  out- 
lining of  the  sinus. 

It  is  always  better  to  include  as  much  of  the 
part  under  clinical  suspicion  as  possible  in  a 
general  survey.  When  the  lesion  has  been 
located  a  subsequent  examination  is  made  for 
more  radiographic  detail. 

The  Stereoeoentgenogr.\phic  Ex.\mina- 

TION   OR   StEREOGR.\PHY 

The  principles  of  this  examination  are  as. 
outlined  in  stereoscopy.  Only  in  this,  the 
plate  method,  two  plates  are  made,  each  from 
a  different  tube  position,  the  focal  point  being 
displaced  two  and  one-half  inches   (6.5  cm.). 

For  its  successful  practise  there  is  neces- 
sary : 

1.  The  maintenance  of  the  undisturbed  re- 
lationship between  the  immobilized  part  and 
the  plate. 

2.  The  shifting  of  the  tube,  the  proper  dis- 
tance and  direction. 

3.  The  proper  view  of  the  radiograms. 
The  examination  may  be  made  horizontally 

or  vertically.  Tlie  shifting  of  the  plate  and 
tube  is  now  done  automatically  liy  many  de- 
vices.    The  tube  is  shifted 


at  right  angles  to 


ri311 


132 


TELEOGRAPHY 


the  long  axis  of  the  object  through  which  it 
is  desired  to  look.  A  certain  var_ving  degree 
of  tilting  becomes  necessary  if  a  cone  or 
cylinder  is  used. 

Both  kidneys  may  be  examined  stereo- 
scopically  on  one  set  of  plates  and  compression 
still  maintained  by  a  device  suggested  by 
Caldwell  and  described  by  Stewart,  which 
consists  of  a  small  modern  frame  having  the 


Fig.   175. — Compression   frame   for  exposures  of 
Abdomen. 

width  of  the  space  between  the  horizontal  arms 
of  the  stand  on  which  the  tube  holder  slides. 
(Fig.  175). 

The  length  is  sufficient  to  allow  for  the  shift- 
ing of  the  tube  and  to  give  firm  support  while 
•compressing  the  abdomen  about  14  inches. 
x\cross  each  end  of  the  frame  a  wooden  bar 
^  of  an  inch  thick,  and  the  same  width  as  the 
end  of  the  frame  is  provided ;  it  extends 
out  over  the  frame  on  each  side  sufficiently 
to  receive  the  arms  of  the  stand  in  hollowed 
ends.  At  each  terminal  of  this  bar  is  placed 
a  metal  clip  which  snaps  over  the  horizontal 


arms  of  the  tube  stand  and  holds  the  frame 
in  position.  This  frame  is  then  windowed 
with  transparent  celluloid  Is  of  an  inch  tly.ck. 

The  frame  is  snapped  into  place  on  the 
arms  of  the  stand,  an  ordinary  No.  B  rubber 
football  bladder,  encased  in  a  canvas  bag,  is 
inflated  and,  placed  on  the  abdomen  of  the 
patient,  beneath  the  celluloid  frame.  As  much 
compression  as  desired  is  now  made,  the  tube 
holder  being  shifted  the  required  distance 
above  without  distvu'bing  the   compression. 

In  chest  radiography,  shifting  of  the  tube 
is  in  the  long  axis  of  the  body,  in  other  words, 
at  right  angles  to  the  ribs.  In  the  vertical 
posture  the  most  useful  device  is  that  which 
displaces  the  tube  downward  for  a  distance  of 
two  and  one-half  inches.  In  the  horizontal 
position,  when  automatic  plate  shifting  tables 


Fig.  177. — Teleroentgenographic  apparatus  for  ac- 
curate adjustment.  It  consists  of  two  upright 
rectangular  frames  of  substantial  construction 
seven  (7)  feet  high.  On  one  upright  of  either 
standard  there  are  corresponding  scales  in 
one-quarter  (;4)  inch  divisions,  the  scales 
being  at  the  same  level  from  ■  the  floor. 
The  frames  to  be  twenty  (20)  inches  wide. 
They  are  set  in  wooden  bases  or  platforms, 
movable  on  tracks  which  are  scaled  so  as 
to  permit  the  estimation  of  the  distance  of 
the  standards  from  each  other.  In  one  frame, 
suitably  counter-weighted,  there  is  a  cellu- 
loid window.  Behind  this,  by  an  arrangement 
similar  to  a  camera  back  there  is  a  fluorores- 
cent  screen,  corresponding  to  the  ground  glass 
of  the  camera,  but  permitting  the  use  of  a 
screen  holder'  for  fourteen  by  seventeen 
(14x17)  inch  plate  or  plate  in  envelope.  In 
the  other  a  lead  covered  tube  box  opening 
six  (6)  inches  in  diameter  fitted  with  a  dia- 
phragm. The  box  is  counterweighted  and  freely 
movable  in  up  and  down  direction.  Both  the 
tube  holder  and  plate  holder  arrangements  are 
fitted  with  clamps  for  fixing  at  certain  heights. 

are   utilized,   the   patient   is   placed    at    right 

angles  to  the  long  axis  of  the  table,  over  the 

Fig.  176.— Method  of  horizontal  stereoscopic  exami-       permeable  window  (Fig.  176).   The  tube  stand 

nation  of  the  chest  m  order  to  obtain  a  displace-       ...  1        ,        7       1  •     •  , 

ment  of  the  tube  in  the  long  axis  of  the  chest.       's    placed    at    the    head,    thus    permittmg    the 


SERIAL  EXPOSURE  AIETHOU 


l.U 


proper  shifting.  Tlie  part  must  be  immobil- 
ized. The  tables  and  tube  stand  must  be  care- 
fully fixed  to  avoid  vibration  during  the  plate 
shifting. 


Fig.  178. — Horizontal  serial  apparatus.  The  table 
is  covered  with  lead,  except  for  an  opening 
4V2  X  5J4  over  which  the  part  to  be  radiographed 
is  placed.     (Hirsch.) 


The  two  expostires  with  a  tube  shifting  of 
two  and  one-half  inches  from  the  median  line 
must  be  made  during  the  cessation  of  respira- 
tory movements.  Where  extreme  rapidity  of 
exposure  is  necessary,  because  of  the  inability 
of  maintaining  inmiohilization.  intensifying 
screens  should  be  used. 

Considerable  latitude  is  permissible  in  the 
amount  of  deviation  permitted  to  obtain  stereo- 
scopic efifects.  It  is  more  important  rather 
to  increase  the  distance  than  to  diminish  it. 
It  is  advisable  to  vary  the  exposure  slightly 
for  the  two  plates.     The  plate  made  with  the 


Fig.  179. — Plate  holding  pan  for  10x12  plate  for 
apparatus.  This  is  slid  from  behind  the  parti- 
tion under  the  opening  in   the  table. 


Fig.    180. — \  iew    irt)ni    within    protective    booth    of 
serial  plate  changing  apparatus.      (Hirsch.) 


shift  of  the  tube  to  the  right  should  be  marked 
(R)  and  the  other  (L).  After  the  two  ex- 
posures have  been  developed,  the  images  may 
be  optically  combined  by  the  many  forms  of 
stereoscopes,  the  \Mieatstone  reflecting  mirror 
being  most  commonly  used.  By  means  of  re- 
ductions, a  hand  prism  stereoscope  may  be 
utilized. 


134 


POLYGRAMS 


Teleroentgenography 

By  orthoroentgenoscopy  it  is  possible,  as 
has  been  shown,  to  minimize  tlie  distortion  in 
the  shadow  of  an  organ,  resulting  in  the  diver- 
gence of  the  rays,  by  outlining  the  structures 
by  the  central  ray.  The  disadvantages  which 
attend  this  method  may  be  overcome  by  mak- 
ing a  permanent  record  on  a  sensitive  plate  by 
a  ray,  which  for  practical  purposes,  is  rela- 
tively parallel.  This  may  be  attained  by  in- 
creasing the  target  plate  distance  to  two 
meters  or  eighty  inches.  While  the  difference 
between  the  size  of  the  heart  shadow  made  at 
the  usual  distance,  fifty  centimeters,  and  the 


Fig.  i8i. — Back  of  plate  holding  pan.  The  pin  is 
made  to  move  on  a  -|-  track,  this  bringing  the 
various  quarters  of  the  plate  under  the  hole  in 
the  table   for  exposure.     (Hirsch.) 

shadow  at  two  meters,  is  over  one  centimeter, 
the  distortion  at  the  latter  distance  is 
negligible.  In  chest  examinations  a  dorso- 
ventral  exposure  is  the  one  usually  made 
with  the  object  of  determining  the  heart  size. 
The  tube  is  focused  at  the  sixth  dorsal  ver- 
tebra. It  is  an  advantage  to  place  lead  markers, 
in  the  supra-sternal  notch,  or  at  the  zi- 
phoid.  It  is  not  necessary  that  the  exposures  be 
very  short,  since  it  is  the  purpose  to  obtain  the 
maximum  dimension,  as  in  diastole.  The  use 
of    an    intensifying    screen    and    a    relatively 


high  tube  is  necessary,  if  detail  and  sharpness 
is  to  be  obtained.  By  the  use  of  a  film  be- 
tween two  screens,  satisfactory  teleroentgeno- 
grams  may  be  made   with    small    apparatus. 


Fig.  182. — Vertical  serial  apparatus.  Patient  is  in 
position  and  plate  is  in  position  ready  for 
exposure.     (Hirsch.) 

Sensitized  paper  may  be  used  with  intensify- 
ing screen.  This  method  is  also  used  for  the 
determination  of  the  size  of  the  female  pelvis. 
A  relatively  long  exposure  and  the  use  of 
intensifying  screens  are  necessary. 


Fig.   183. — Kimoroentgenographic  apparatus. 

To  be  valuable  as  an  accurate  method  for 
comparative  purposes,  it  is  essential  that  an 


KIMORADIOGRAPHY 


135 


exact,  definite  techniqvie  be  adopted,  so  that 
not  only  distance  but  tube  arrangement  be 
similar  for  all  cases. 

It  is  important  that  the  subject  be  properly 
placed,  since  slight  turning  or  displacement 
may  result  in  error.  The  tube  must  be  acciu"- 
ately  focused  on  a  standard  point.  Various 
mechanical  devices  have  been  made  to  obtain 
the  accurate  arrangement  for  this  work.  De- 
tailed exactness  is  necessary  if  the  measure- 
ments are  to  be  of  any  value.  By  means 
of  two  uprights  moving  on  tracks,  one  for 
the  holding  of  the  plate  and  the  other  for  tube, 
accurate  centering  and  fixation  mav  be  ob- 
tained (Fig.  177). 


Fig.   184. — Roeiitgenkymogram  of   the  left  ventricle, 
showing   four  cardiac  pulsations.      (.Rosenthal.) 


Serial  Exposures 

These  are  of  value  for  the  study  of  the 
changing  aspect  of  movable  organs,  as  heart 
diaphragm,  and  organs  of  gastro  intestinal 
tract. 

For  this  purpose,  a  mechanism  is  utilized, 
which  will  rapidly  bring  a  full  size  plate 
opposite  the  part  radiographed,  properly  ex- 
pose it  and  then  remove  it  safely  from  the 
action  of  the  rays,  while  another  plate  goes 
into  the  proper  position  for  exposure ;  the 
main  problem  is  a  mechanical  one.  It  may 
be  done  automatically  (Fig.  185),  or  by  hand 
(Figs.  178  to  181).   ' 

The  plates  may  later  be  viewed  individually 
or  they  may  be  transposed  to  stnaller  continu- 
ous cinema  films  and  a  false  moving  picture 
may  be  made,  by  throwing  them  rapidly  on  a 
screen  by  a  projection  apparatus.  Another 
valuable  method  of  study  is  to  make  a  com- 
posite tracing  of  them  and  noting  the  devia- 
tions in  contour  which  indicate  the  movement. 

Polygram 

Several  exposures  in  rapid  succession  are 
made  on  the  same  plate.  The  difficulty,  how- 
ever, arises  in  tracing  these  exposures,  when 
more  than  five  are  made,  but  for  gross  effects 
this  method  has  a  certain  value,  because  it 
permits  the  determination  of  the  extent  of 
the  mobility  of  the  particular  organ  or  part 
of  the  organ.  It  is  mostly  used  in  the  study 
of  gastric  peristalsis  but  the  study  of  the  heart 
activity  may  also  be  made  in  this  way. 

Kiinoroentgcuography 

Roentgenography  of  the  pulsations  of  the 
various  heart  chambers  through  slits  in  an 
impermeable  partition  upon  a  movable  record- 
ing surface,  the  record  being  in  the  form  of  a 
pulsation  curve.  This  method  was  first  de- 
scribed by  Gocht  and  Rosenthal. 

The  patient  stands  with  his  chest  against  a 
lead  screen  in  which  there  is  a  narrow  hori- 
zontal slit,  corresponding  to  the  position  of 
that  portion  of   the  heart  to  be  studied.     A 


136 


KIMORADIOGRAPHY 


fluorescent  screen,  placed  behind  the  sht,  will 
show  a  brightly  illuminated  area  correspond- 
ing to  the  lung  and  a  portion  of  the  heart. 
The  junction  of  the  light  and  the  dark  field 
may  be  considered  as  a  line  in  continual  move- 
ment, corresponding  to  the  pulsations  of  the 
heart.     If,  now,  a  photographic  film  or  plate 


The  skiagram  (Fig.  184)  shows  a  Roent- 
genkymogram  of  the  left  ventricle.  The  main 
graph,  running  across  the  plate,  represents 
the  movement  of  the  left  ventricle.  The  ver- 
tical lines  are  shadows  of  those  parts  of  the 
body  which  remain  at  rest — ribs,  marks  on 
the  thorax,  etc.     The  wavy  lines,  more  or  less 


Fig.  185. — Bioroentgenographic  apparatus.  This  apparatus  consists  of  a  framework  holding  thirty- 
two  (32)  plate  holders  with  means  for  rotating  the  framework  so  as  to  bring  the  plates  suc- 
cessively in  line  before  an  aluminum  window,  exposing  the  plate  so  brought  to  rest,  automatically 
to  the  x-rays  for  a  brief  period  during  which  the  rotating  framework  is  to  remain  still,  and  means 
for  preventing  the  further  exposure  of  the  plate  by  rotating  the  framework  so  as  to  rotate  the  plates 
away  from  the  aluminum  window  and  place  an  unexposed  plate  in  position.  A  timing  device  is 
provided  whereby  the  entire  thirty-two  (32)  exposures  may  be  automatically  made.  The  whole 
is  enclosed  in  an  x-ray  proof  cover  placed  on  a  stand  adjustable  in  the  vertical  direction.     (Hirsch.) 


is  moved  across  the  slit,  a  permanent  record 
will  be  obtained  of  the  movement  of  the  por- 
tion of  the  heart   (Fig.   183). 

Graphs  or  curves  of  the  movement  of  sev- 
eral portions  of  the  heart,  the  left  ventricle, 
the  right  auricle,  the  aorta  and  the  pulmonary 
artery  may  be  obtained  simultaneously. 


parallel  to  the  cardiac  curves,  are  shadows 
of  intrathoracic  organs,  bronchi,  blood  ves- 
sels, glands,  etc.,  parts  which  either  have  an 
individual  movement  or  move  by  the  trans- 
mitted pulsations  of  the  heart.  The  time  data 
of  the  curve  may  be  marked  on  the  plate  in 
one-fifth    seconds. 


CHAPTER  XV 
THE  SILVER  BROMIDE  PLATE 

The  variety  of  examination  having  been  de- 
termined upon,  the  plate  is  now  prepared. 
The  photographic  plate  consists  of  one  or 
more  layers  of  bromide  of  silver,  spread  on 
glass  or  celluloid.  The  action  of  the  x-ray  on 
this  emulsion  is  similar  to  that  of  light. 

The  fastest  (most  sensitive)  plate  is  not 
always  the  most  desirable  for  x-ray  purposes. 
The  qualities  which  a  sensitive  plate  should 
possess  are  as  follows : 

1.  The  glass  should  be  of  proper  quality 
(free  from  lead),  of  proper  thickness,  not  ex- 
ceeding one-half  millimeter,  free  from  flaws 
and  have  bevelled  edges. 

2.  The  emulsion  should  be  in  a  gelatine  base, 
which  will  not  deteriorate  with  age,  disinte- 
grate by  the  action  of  the  x-rays  or  separate 
from  the  glass  under  the  processes  of  develop- 
ment. 

3.  The  emulsion  should  be  evenly  spread  in 
two  or  more  layers  with  the  exclusion  of  air 
bubbles  between  them. 

4.  The  developed  plate  should  show  no 
marked  variation  in  density  over  an  area  ex- 
ceeding one  inch  square,  should  be  free  from 
defects  and  should  show  a  fine  grain. 

5.  The  sensitizer  used  in  the  bromide  of 
silver  emulsion  should  not  be  excessive  in 
quantity  and  should  be  easily  removable  in  the 
fixing  bath. 

6.  The  emulsion  should  be  capable  of  rapid 
solution  in  hyposulphite  solution. 

7.  Fogging  should  not  take  place  in  the  un- 
exposed plate  (due  to  rapid  overipening)  or 
from  prolonged  development.  The  extreme 
sensitiveness  of  the  plate  makes  necessary  the 
observance  of  precautions  in  their  preparation 
for  use  in  the  x-ray  examinations.  The  sen- 
sitive emulsion  of  the  plate  may  be  affected  by 

1.  Moisture 

2.  Heat 

3.  Friction 


4.  Chemical  vapors 

5.  Electric  sparks. 

The  plates,  therefore,  are  stored  in  a  cook 
dark,  dry  room,  protected  from  the  effects  of 
the  x-rays. 

The  Plate  is  Placed  in  Envelopes 
For  use  in  x-ray  examinations  the  plate  is 
placed  either  in  an  envelope  plate  holder 
or  in  contact  with  an  intensifying  screen  in  a 
cassette.  This  should  preferably  be  done  in 
absolute  darkness  or  by  the  dim  light  of  a  ruby 
lamp.  For  the  identification  of  the  sensitive 
side  of  the  plate,  a  certain  arbitrary  method 
of  placing  the  plate  in  the  envelope  must  be 
adopted.  Two  envelopes  are  used,  one  red 
and  one  black.  The  almost  universally 
used  method  is  to  place  the  sensitive  emulsion 
to  the  smooth  (non-flapped)  side  of  the  black 
envelope,  placing  the  flap  end  at  the  bottom  of 
the  outer  red  envelope  and  keeping  the  smooth 
side  of  the  black  to  the  smooth  side  of  the 
red.  Thus,  the  sensitive  side  of  the  plate  is 
to  the  smooth  side  of  the  red  envelope  and 
but  one  flap  is  uppermost.  The  same  pro- 
cedure holds  true  for  films.  Where  double 
coated  films  are  used,  these  precautions  are, 
of  course,  unnecessary.  Care  must  be  taken 
in  removing  the  plates  from  the  box  (which 
should  be  stored  standing  on  edge),  to  handle 
the  plate  by  its  edges  in  order  to  avoid  finger 
marks,  and  in  placing  the  plate  in  the  envelope 
to  avoid  rubbing  the  emulsion  with  the  paper. 
Before  placing  in  the  envelope  the  plate  should 
be  lightly  brushed  down  with  a  soft  camel's 
hair  brush  to  remove  the  dust. 

Special  plate  holders  have  gone  out  of  use 
to  a  considerable  extent,  except  as  containers, 
for  screens. 

Intensifying  Screens 
The  fluorescent  properties  which  certain 
salts  manifest  when  exposed  to  x-rays  are 
utilized  for  the  purpose  of  intensifying  the 
eft'ect  of  the  x-rays  on  the  photographic  emul- 
sion and  thus  reducing  the  length  of  exposure. 
Since  the  effect  is  an  actinic  one,  that  colored 


[1371 


138 


THE  INTENSIFYING  SCREEN 


fluorescence  is  sought,  which  has  a  preponder- 
ance of  bluish  white  rays. 

Calcium  tungstate  gives  the  desirable  fluor- 
escence and  the  screens  now  used  consist  of 
some  form  ( usually  the  amphorous,  reduced 
to  a  fine  powder)  of  pure  calcium  tungstate 
or  a  combination  of  this  and  other  salts  sus- 
pended in  an  agglutinant  and  coated  upon  a 
suitably  prepared  cardboard.  For  the  proper 
and  successful  use  of  such  an  intensifying 
screen  several  conditions  are  necessary. 

1.  Absolute  contact  between  the  sensitive 
surfaces  of  screen  and  plate.  The  difficulty 
of  obtaining  this,  when  the  screen  is  inserted 
into  the  paper  envelope  and  thus  applied  to 
the  part,  has  brought  into  use  the  screen 
cassette.  This  may  be  of  cardboard  and  wood 
or  of  metal  (aluminum).  The  cassette  should 
be  light-proof,  the  side  of  the  recess  being 
lined  with  wood,  easily  opened  and  closed  by 
a  hinged  back,  not  too  heavy  or  too  thick.  It 
is  preferable  that  the  front  side  be  cov- 
ered with  cardboard  or  black  celluloid  instead 
of  metal.  The  screen  is  usually  affixed  to  the 
inside  of  the  felt-covered  hinged  back  of  the 
cassette.  The  felt  easily  adjusts  itself  to  the 
variations  in  thickness  of  the  glass  plates. 
The  plate  is  placed  sensitive  side  up  in  the 
cassette  and  the  hinged  back  of  the  cassette  is 
now  closed  and  kept  in  contact  with  the  screen 
by  springs  on  the  outside  of  the  hinged  back. 
Two  metal  springs  are  sufficient  if  the  cassette 
is  properly  made.  The  more  absolute  the  con- 
tact and  the  firmer  the  pressure  between  screen 
and  plate,  the  more  sensitive  is  the  response 
of  the  screen  and  the  better  the  definition. 
When  the  screen  is  thus  placed  in  position  for 
exposure  the  rays  penetrate  the  glass  side  of 
the  sensitive  plate  and  aft'ect  the  emulsion  and 
then  receive  the  added  elTect  of  the  fluor- 
escence of  the  screen.  The  objection  to  this 
method  of  exposure  through  the  sensitive  plate 
is  the  absorption  of  a  certain  quota  of  the  rays 
by  the  glass  of  the  plate.  In  some  brands  of 
plates  this  may  be  so  considerable  as  to  be- 
come an  important  factor.  In  the  best  plates 
the  absorption  is  a  negligible  quantity.  The 
other  objection  is  the  reversal  of  the  image, 
which  results.  Some  of  the  cassettes  are  so 
constructed   that   the    rays   pass   through    the 


screen  first.  This  is  also  objectionable  be- 
cause of  the  granular  appearance  of  the  result- 
ing plate,  ^^'hen  certain  forms  of  cakium 
tungstate  are  used  their  absorption  of  the  rays 
may  be  much  greater  than  the  glass  of  the  plate. 

2.  A  clean  screen  surface.  The  removal  of 
dust  from  the  surface  of  the  screen  and  from 
the  sensitive  surface  of  the  plate.  This  is 
important,  not  only  because  the  fluorescence 
intercepted  by  the  light  will  cause  a  mottling 
of  the  negative  but  also  to  prevent  injury  of 
the  screen.  The  gentle  cleaning  is  best  done 
by  a  piece  of  soft  cotton  cloth  or  a  camel's 
hair  brush.  The  rubbing  should  be  gentle 
and  done  in  one  direction.  Developer  stains, 
scratches,  abrasions,  all  may  be  prevented  by 
care  during  manipulations. 

3.  The  "  loading  of  the  screen  "  just  before 
the  exposure  and  "  unloading "  immediately 
after  exposure.  The  received  plate  is  to  be 
kept  in  a  light-proof  receptacle  until  develop- 
ment. This  will  prevent  a  haziness  and  slight 
fogging  of  the  image. 

4.  The  frequent  "  airing  "  of  the  screen  to 
prevent  softening  of  the  sensitive  surface. 

5.  The  occasional  cleansing  of  the  screen 
surface  by  peroxide  of  hydrogen. 

6.  The  proper  exposure  of  the  screen.  The 
most  frequent  error  in  this  respect  is  over- 
exposure. The  various  screens  are  able  to 
reduce  the  exposure  from  500  to  900  per  cent. 
The  most  sensitive  screens  are  as  unpractical 
as  the  slowest.  Where  the  intensity  of  the 
x-ray  is  relatively  feeble,  two  intensifying 
screens  ma\-  be  used,  one  to  the  sensitive  sur- 
face and  one  to  the  back  of  a  film.  The  eflfect 
is  still  further  intensified  if  a  double  coated 
( Dupli-Tized)  film  is  used,  both  sides  of  the 
latter  being  covered  by  emulsion. 

The  screen  is  more  actively  excited  by  med- 
ium and  soft  rays  than  by  hard.  To  obtain 
the  maximum  fluorescent  eftect  it  is  necessary 
that  a  considerable  percentage  of  the  ray  be 
absorbed,  and  thus  the  short-waved  x-rays 
are  transformed  into  longer-waved  actinic 
rays.  The  thicker  the  layer  of  tungstate  in 
the  screen  the  better  it  is  able  to  respond  to 
harder  rays. 

7.  The  proper  development  of  the  screen 
plate  (see  development). 


CHAPTER  XVI 
POSTURES  AND  POSITIONS 

The  plate  )iiust  be  placed  in  proper  contact 
icith  and  i)i  proper  relationship  to  the  part  to 
he  examined. 


The  plate  is  placed  with  the  smooth  side  of 
the  envelope  and  therefore  the  sensitive  side 
of  the  plate  against  the  part.  The  exception 
to  this  relationship  is  the  arrangement  when 
the  screen  is  used,  under  which  conditions  the 
glass  side  of  the  plate  is  nearer  the  part  to  be 
radiographed. 


Fig.   i8o. — First  oblique   Dorso-ventral   arrangement.      Fid.   187. — First  oblique  \'entro-dorsal  arrangement. 

[1391 


140 


POSTURES 


The    part    is    nozc    placed    in    position    for 
examination. 

A  certain  definite  arrangement  must  be 
effected  between  the  tube,  the  part  to  be 
examined   and   the   recording   media. 

The  Roentgenological  examination  is  not  a 
haphazard  procedure.  In  the  production  of 
the  radiograph  of  any  part,  it  is  necessary 
that  a  definite  technique  be  followed,  firstly, 
in  the  arrangement  of  the  relationships  be- 
tween object,  recording  surface  and  central 
ray  and  secondly  in  the  delineation  of  the 
structures  in  shadows  having  color  tones  of 
certain  value.  Such  relationships  and  radio- 
graphic appearances  having  been  established, 
the  resulting  views  constitute  what  is  known 
as  normal  radiograph\.  This  does  not  refer 
to  the  anatomic  condition  but  is  a  radio- 
graphic term  indicating  that  the  proper  tech- 
nique has  been  followed  in  the  making  of  the 
examination. 

The  first  condition  depends  on  the  observ- 
ance of  certain  rules,  regarding  the  relation- 
ship of  the  central  ray  to  certain  bony  land- 
marks with  the  parts  in  definite  postures.  The 
second  depends  on  the  utilization  of  the  proper 
ray  quality  and  quantity  and  will  be  discussed 
under  the  heading  of  exposures. 

Postures 

The  examination  of  the  body  may  be  made 
in  various  directions,  this  being  necessary  for 
the  isolation  of  the  body  structures  overlying 
each  other.  The  relation  of  the  tube  to  the 
recording  surface — plate  or  screen — may  be 
either  centric  or  excentric.  In  the  former  the 
central  ray  falls  perpendicularly  to  the  record- 
ing surface,  while  in  the  excentric  arrange- 
ment it  does  not.  The  terms  applied  to  indi- 
cate the  relation  of  the  tube  to  the  body  are 
such  as  give  the  ray  direction.  Thus  the 
designation  dorso-ventral  means  that  the  rays 
are  passing  through  the  dorsum  ventrally  and 
ventro-dorsal  indicates  the  reverse.  Thus 
sinestro-dextral  view  means  that  the  tube  is 
to  the  left  and  the  recording  surface  at  the 
right. 


examination. 


Centric  Arrangetncnt 

Depending  upon  the  direction  of  the  ray,  the 
view  is  obtained  in  various  planes.  Th%  sagit- 
tal view  is  obtained  by 

1.  Dorso-ventral  ~^ 

or  >  examination. 

2.  Ventro-dorsal  J 

The  frontal  view  is  obtained  by  a 

1.  Sinestro-dextral 

2.  Dextro-sinestral 

The  oblique  views  are  obtained  by  the  ven- 
tro-dorsal or  dorso-ventral  examination,  but 
with  the  part  turned  so  that  the  ray  passes 
either  in  that  diameter  which  extends  from 
the  right  side  ventrally  to  the  left  side  dor- 
sally  or  from  the  left  side  ventrally  to  the 
right  side  dorsally. 

For  the  sake  of  simplicity  the  oblique  diam- 
eters have  been  numbered.  That  oblique 
diameter  which  passes  from  the  right  side 
ventrally  to  the  left  side  dorsally  being  called 
the  first  and  that  oblique  diameter  which 
passes  from  the  left  side  ventrally  to  the  right 
side  dorsally  being  called  the  second.  The 
first  oblique  corresponds  to  the  position  a 
fencer  assumes  in  fencing.  Since  the  ray  may 
pass  through  the  oblique  diameters,  either  ven- 
tro-dorsally  or  dorso-ventrally,  there  are  four 
oblique  views. 

1.  Ventro-dorsal  first  oblique,  tube  is  in 
front  and  to  the  right,  and  the  plate  or  screen, 
behind  and  to  the  left  (Fig.  187). 

2.  Dorso-ventral  first  oblique,  tube  behind 
and  to  the  left  and  the  recording  surface  in 
front  and  to  the  right  (Fig.  186). 

3.  Ventro-dorsal  second  oblique,  tube  in 
front  and  to  the  left,  and  the  recording  surface 
behind  and  to  the  right  (Fig.  188). 

4.  Dorso-ventral  second  oblique,  tube  be- 
hind, and  to  the  right,  and  the  recording  sur- 
face in  front  and  to  the  left  (Fig.  188). 

In  these  various  centric  views  it  is  the 
object  which  is  rotated,  the  relation  of  plate 
to  tube  remaining  unchanged. 

Excentric  Viezvs 
The  views  to  be  enumerated  are  called  ex- 
centric because  the  central  ray  no  longer  falls 


CENTRIC  AND  EXCENTRIC  VIEWS 


141 


perpendicularly  to  the  plate.  In  these  excen- 
tric  views  the  tube  may  be  displaced  either 
above,  below,  to  the  right  or  to  the  left  of 
the  center  of  the  screen  or  plate.  When  dis- 
placed laterally,  the  position  is  right  or  left 


Left  Excentric  means  that  the  plate  or  screen 
is  placed  dorsally  in  the  median  line  and  the 
tube  is  placed  in  front  and  to  the  left  of  the 
median  line.  Ventro-Dorsal  Right  Excentric 
means  that  the  tube  is  in  front  and  to  the  right 


Fig.   i88. — Second  oblique  Ventro-dorsal  and  Dorso  ventral    arrangement 


excentric  but  when  displaced  vertically,  su- 
perior or  inferior  excentric.  Thus  Dorso- 
Ventral  Left  Excentric  position  means  that 
the  plate  or  screen  is  placed  ventrally  and  that 
the  tube  is  dorsal  and  to  the  left  of  the  median 
line  and  Dorso-Ventral  Right  Excentric 
means  that  the  tube  is  still  dorsal  but  shifted 
to  the  right  of  the  median  line.   Ventro-Dorsal 


of  the  median  line.  The  terms  Ventro-Dorsal 
Superior  Excentric,  Dorso-Ventral  Inferior 
Excentric,  Dorso-Ventral  Superior  and  Ven- 
tro-Dorsal Inferior  Excentric  explain  them- 
selves. 

Tube  Position 

With  light  as  the  source  of  illumination  its 
point  of  origin  and  distance  from  the  object, 


142 


TUBE  POSITION 


being  known,  the  shape  and  size  of  the  shadow 
cast  by  any  object  may  be  calculated  mathe- 
matically. If  the  conditions  could  be  repro- 
duced with  an  x-ray  this  might  also  be  done 
and  the  resulting  shadows  follow  the  laws  of 
those  produced  by  light. 

Depending  on  the  relationship  of  the  source 
of  illumination  to  the  object,  the  shadow  may 
or  may  not  have  the  diameters  of  the  object 
itself.  When  it  has  it  may  be  called  a  true 
shadow.  When  its  diameters  are  larger  or 
smaller,  it  may  be  called  a  false  shadow. 

From  the  focal  point  on  the  target  the 
x-rays,  traveling  in  straight  lines,  diverge  in 
all  directions.  That  ray  which  is  given  off 
at  right  angles  to  the  tube  axis,  and  falls  per- 
pendicularly to  the  recording  surface  is  the 
central  rav,  the  rest  are  divergent.    Anv  struc- 


FiG.  189. — The  rays  emanating  from  A  give  a  cen- 
tric view.  The  rays  from  B  give  an  infero- 
superior  e.xcentric. 

ture  interposed  in  their  path  casts  a  more  or 
less  distorted  shadow,  depending  on  the  rela- 
tion between  the  source  of  illumination,  the 
object  and  the  recording  surface.  There  are 
several  roentgenological  axioms  covering  this 
relationship,  which  are  constantly  applied  both 
in  technique  and  interpretation. 

Relationship  of  Object  to  Recording  Surface. 

1.  The  nearer  the  object  is  to  the  recording 
surface,  the  truer  and  sharper  its  shadow. 
(Fig.  191). 

Practical  Application:  The  part  to  be  studied 
should  be  placed  as  near  the  plate  as  possible, 


thus  a  sharper  shadow  of  the  fibula  or  the 
fifth  metatarsal  is  obtained  with  the  plate  at 
the  external  aspect  of  the  leg  than  *at  the 
internal — of  the  clavicle  in  the  dorso-ventral 
view  than  in  the  ventro-dorsal. 


Fig.  190. — The  tube  mesially  placed  is  in  centric 
ventro-dorsal  position.  The  tubes  to  the  right 
and  left  are  in  the  excentric. 

This  axiom  is  utilized  in  the  localization 
of  foreign  bodies  in  the  tissues ;  for,  if  the 
shadow  of  the  foreign  body  is  smaller  and 
sharper,  with  the  screen  at  the  anterior 
aspect,  then  it  is  located  more  anteriorly  than 
posteriorly.  In  the  study  of  the  relationship 
of  fragments  of  a  fracture,  where  views  at 
right   angles    cannot   be   made,    the    fragment 


Fig.  191. — A.xiom  I  and  II.  The  shadow  of  the 
sphere  at  a  is  smaller  and  sharper  than  the 
shadow  at  b.  The  shadow  of  the  object  with 
the  tube  at  c  is  smaller  and  sharper  than  with 
tube  at  d.     (Grashey.) 

with  the  larger,  hazier  and  more  distorted 
shadow  is  the  further  from  the  recording 
surface. 


RADIOLOGICAL  AXIOMS 


143 


Corollary:  The  closer  an  object  lies  to  the 
recording  surface,  the  less  the  deviation  of  its 
shadow  by  displacement  of  the  source  of 
illumination. 


Fig.   192 

Application :  This  axiom  is  utilized  in  the 
localization  of  foreign  bodies.  Thus,  with 
a  certain  deviation  of  the  source  of  illumina- 
tion, the  object  furthest  from  the  recording 
surface  will  move  most  while  that  which  lies 
nearest  the  recording  surface  will  move  least 
or  not  at  all. 

Relationship    of   Source    of    Illuiiiiiiation    to 
Object. 

2.  The  further  the  tube  is  from  the  object 
the  truer  and  the  sharper  will  be  its  shadow. 
(Fig.  191). 


Fig.  193. — The  shadow  of  the  sphere  cast  by  the 
divergent  ray  is  larger  than  the  shadow  of  a 
similar  sphere  outHned  by  the  central  bundle. 
Increasing  the  target  plate  distance  diminishes 
the  distortion.     (Grashey.) 

Corollary :  With  a  part  at  a  distance  from 
the  recording  surface,  the  distortion  is  mini- 
mized by  increasing  the  tube  object  distance. 


Practical  Afflicalioii:  The  tube  distance 
should  be  such  as  to  give  a  minimum  distor- 
tion. Twenty  inches  (50  cm.j  target-skin 
distance  has  been  adopted  for  general  pur- 
poses. When,  because  of  plaster  cast  or  ban- 
daging it  is  impossible  to  bring  the  part  in 
close  apposition  to  the  plate,  the  tube  plate 
distance  is  increased.   When  it  becomes  neces- 


FlG. 


194. — Schematic  representation  of  the  shadow 
of  a  series  of  oral  objects,  like  the  lumbar  ver- 
tebra. The  shaded  parts  represent  the  shadows 
of  the  lower  surface,  that  nearest  to  the  record- 
ing surface,  hence  sharper  and  smaller ;  the 
lighter  parts,  the  shadows  of  the  upper  surfaces 
furthest  from  the  recording  surface,  hence  hazy 
and  larger.     (Grashey.) 


sary  to  estimate  the  diameters  of  a  structure 
— the  distortion  is  reduced  to  a  minimum  by  a 
long  tube-plate  distance.  This  is  usually  two 
meters.     (Teleroentgenography) . 

Note :  The  intensity  of  the  illumination 
diminishes  in  inverse  ratio  to  the  square  of 
the  target-plate  distance. 


Corollarv 


\'arying    the    target    recording 


144 


RADIOLOGICAL  AXIOMS 


surface  distance  will  cause  a  deviation  of  the 
shadow  of  an  object.  The  deviation  will  be 
greater  the  further  away  the  object  lies  from 
the  recording  surface   (Fig.   192). 

Relationship  of  Object  to  Central  Ray. 

3.  The  nearer  the  object  lies  to  the  central 
ray.  the  truer  and  sharper  its  shadow  (Fig. 
193). 

The  greater  the  divergence  of  the  ray,  the 
greater  the  distortion  of  the  shadow  of  the 
object  transilluminated  by  it.  The  distortion 
due  to  this  divergence  of  the  ray  may  be  mini- 
mized by  increasing  the  tube-object  distance. 


Fig.  195. — The  object  and  plate  are  placed  at  an 
angle  to  the  horizontal  plane  with  a  resulting 
distortion  of  the  shadow  of  the  object.  This 
would  be  equivalent  to  placing  the  object  in 
the  path  of  a  divergent  beam  (Fig.  196a),  and 
constitute  excentric  views.     (Grashey.) 


Practical  Application:  In  the  examination 
of  the  vertebrae  a  true  shadow  will  be  cast 
by  the  body  of  that  one  vertebra  which  lies 
-at  right  angles  to  the  central  bundle,  and  only 
■one  intervertical  space  is  clearly  seen,  viz., 
the  one  which  is  directh'  in  the  path  of  the 
central  ray  (Figs.  193,  194).  The  distortion 
will  be  progressively  greater  in  the  verte- 
brae, the  further  they  are  from  the  one 
transilluminated  by  the  central  ray.  There- 
fore, either  the  target  plate  distance  must  be 


increased  ( with  proportionate  increase  in  ex- 
posure and  fogging  due  to  secondary  radia- 
tion) or,  with  the  aid  of  cylinders  and^dia- 
phragms  but  two  vertebrae  be  examined  at 
each  exposure. 

The  object  may  lie  with  its  long  axis  parallel 


Fig.  196(a). — A  similar  distortion  to  that  obtained 
in  Fig.  195,  is  obtained  by  directing  an  oblique 
ray  through  the  object.  These  purposeful  distor- 
tions are  used  in  radiography  as  in  examination 
of  sinuses  of  head  or  parts  of  shoulder  girdle. 

Fig.  196  (b). — The  tube  is  tilted  so  as  to  bring  the 
central  ray  through  the  central  axis  of  the 
cylinder  and  perpendicular  to  the  recording  sur- 
face, and  a  relatively  undistorted  centric  view 
is  obtained.     (Grashey.) 


or  perpendicular  to  the  central  ray.  The  more 
nearly  perpendicular  the  long  axis  of  the 
object  lies  to  the  central  ray,  the  truer  and 
sharper  the  shadow.  The  smallest  shadow  of 
an  object  is  obtained  by  placing  it  with  its  long 


Fig.  197. — Compression  of  the  abdomen  with  cylin- 
der. No  actual  compression  has  really  taken 
place,  because  of   sagging  of  the  abdomen. 

axis  parallel  to  the  central  ray.  \Mien  the 
object  lies  obliquely  to  the  horizontal  plane 
there  is  distortion  of  the  shadow,  and  the  re- 


IMMOBILIZATION 


145 


cording  surface  should  be  placed  ])arallel  to  it 
and  the  central  ray  directed  at  right  angles  to 
the  recording  surface,  if  a  centric  view  is  to  be 
obtained  (Fig.  196-b). 

The  shadow  of  an  object  which  lies  with  its 
long  axis  parallel  to  the  plane  of  the  recording 
surface  will  show  a  minimum  alteration  by 
tube  deviation,  as  compared  to  an  object  lying 
obliquely. 


Fig.  198. — The  interposition  of  a  permeable  material, 
loofah  sponge,  rubber  ball  or  pad  permits  actual 
compression. 

The  factors,  therefore,  upon  which  the 
definition  of  the  shadow  depends  (referring 
to  arrangement  only)   are : 

1.  Proximity  of  the  tube  to  the  object. 

2.  Proximity  of  the  object  to  the  recording 
surface. 

3.  Immobility  of  tube,  part  and  recordiiig 
surface. 

The  first  will  be  discussed  under  exposure 
and  the  second  and  third  will  be  discussed  to- 
gether under  immobilization. 

The  Part  is  Iiiiiiiobiliccd. 

Immobilization  may  be  active,  as  when  the 
chest  walls,  lung  structures  or  kidneys  are 
vokmtarily  immobilized  by  the  cessation  of 
respiration,  or  passive,  as  when  the  part  is 
placed  in  a  certain  posture  and  kept  in  a  fixed 
position  by  the  use  of  immobilization  ap- 
paratus. 

It  is  advisable  to  always  practise  passive 
immobilization  even  when  instantaneous  ex- 
posure is  made.  The  immobilization  should 
aim  to  bring  the  part  in  as  close  proximity 


to  the  recording  surface  as  possible.  To  ac- 
complish this  end,  there  is  necessary  posture 
and  pressure. 

Immobilization  is  simplified  by  placing 
the  part  in  as  comfortable  a  position  as 
possible  (the  muscles  relaxed  and  the  part 
supported).  The  horizontal  posture  is  usually 
better  adapted  to  accomplish  this  end  than  the 
vertical.  The  mental  calm  of  the  patient  is 
conducive  to  immobilization  and  this  necessi- 
tates an  assurance  of  the  painlessness  of  the 
examination  and  the  phenomena  associated 
with  it. 

As  will  later  be  shown  certain  postures  are 
necessary  for  the  proper  delineation  of  the 
structures  of  the  body.  These  postures  are 
definite  and  because  in  their  determination 
a  consideration  of  the  comfort  of  the  patient 
must  play  a  part — they  often  demand  con- 
siderable ingenuity  on  the  part  of  the  invest!-, 
gator  for  their  accomplishment. 

By  the  use  of  sand  bags,  bandages,  binders 
and  numerous  mechanical  appliances,  the  part 
may  be  passively  immobilized.  The  sand  bags 
are  placed  above  and  below  the  part  to  be  ex- 
amined.    A  broad  canvas  band,  weighted  at 


*^ 

Itm' 

Fig.  199. — Device  for  holding  feet  for  radiography 
of  parts  of  leg  or  thighs  or  hip,  so  as  to  obtain 
the   necessary   inversion. 


either  end,  may  render  efficient  service,  the 
band  being  placed  directly  over  the  part.  There 
are  numerous  mechanical  appliances  to  fix 
the  parts  and  permit  reproduction  of  posture 
under  definite  conditions.  The  simplest  and 
commonest  method  of  direct  immobilization 
and   compression    is   bv   cones   and   cviinders, 


146 


IMMOBILIZATION 


furnished  with  ail  modern  tube  stands.  These 
cylinders,  provided  as  they  are  with  dia- 
phragms, are  also  of  assistance  in  cutting  off 
the  scattered  and  secondary  radiations  which  as 
has  been  pointed  out  have  no  definite  direction 
and  serve  only  to  blur  and  distort  the  sharpness 
of  the  shadow.  When  utilized  properly,  par- 
ticularly when  an  interposed  material,  as 
loofah  or  rubber  bag,  is  used  the  result  is  an 
increase  in  detail  and  definition  of  the  tissues. 

The  disadvantages  of  the  metal  cylinders 
or  cones  are  the  inability  of  obtaining  in 
certain  parts  of  the  body  as  the  shoulder  ap- 
proximation of  cylinder  to  part,  the  painful 
pressure  of  the  metal  parts  and  the  sagging 
of  flaccid  parts  of  abdomen  into  the  cone. 
By  the  use  of  strips  of  rubber  tubing  cir- 
cularly disposed  about  the  rim  of  the  cylinder, 
the  interposition  of  loofah  sponges,  inflated 
rubber  balls,  or  pillows  of  cotton  or  sheep's 
wool  the  disadvantages  may  be  nullified. 

Where  compression  is  necessary  in  stereo- 
scopy,  the  inflated  rubber  bag  may  still  be 
utilized,  the  shifting  being  possible  because  of 
the  elasticity  of  the  ball,  when  the  compression 
is  not  too  great.  Otherwise  the  compression 
is  made  through  the  agency  of  a  canvas  frame, 
the  shifting  tube  moving  independently  of 
the  compressing  ball. 

The  inflated  rubber  ball  having  but  one 
seam  (the  innerpart  of  a  basket  ball)  is  of  great 
value  for  compression  in  kidney  examinations. 
It  pushes  the  intestine  out  of  the  way,  immobil- 
izes the  kidney  and  suppresses  respiratory 
movements.  If  a  stereoscopic  examination 
becomes  necessary,  pressure  may  be  made  by 
a  frame. 

The  diaphragmed  cone  or  cylinder  also  has 
the  disadvantage  that  it  narrows  the  extent 
of  the  radiated  surface  and  where  certain  parts 
are  to  be  shown  an  increased  tube  object 
distance  becomes  necessary. 

To  estimate  the  diameter  of  circle  exposed 
with  a  diaphragm  of  known  diameter: 

Radius  of  diaphragm=a 

Target  diaphragm  distance=b 

Target  plate  distance=^c 


Radius  of  area  covered^d 
a:b:  :c  :d 

If  the  central  ray  is  directed  to  a  certain 
area  the  number  of  ravs  originating  from  the 


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Fig.  200. — This  shows  the  diameter  of  the  circle 
exposed  to  the  action  of  the  x-ray  when  the 
various  size  diaphragms  are  used  at  varying 
distances  from  the  plates.  If  an  8x10  plate  is 
to  be  used,  it  is  necessary  to  find  the  smallest 
circle  that  will  accommodate  this  plate.  This  is 
determined  by  taking  the  square  of  the  width, 
8  inches,  equals  64,  and  the  square  of  the  length 
10  inches,  equals  100 ;  the  sum  of  these  is 
164.  The  square  root  of  this  shows  that  the 
plate  will  go  inside  a  circle  approximately  13 
inches  in  diameter.  Referring  to  the  table 
and  noting  at  the  bottom  of  the  bars  the 
diameter  of  the  circle  exposed  and  following 
up  between  12  and  14  we  find  that  the  line 
drawn  from  the  center  of  the  tube  on  the 
outside  edge  of  the  diaphragm  crosses  be- 
tween 12  and  14  at  the  line  marked  27,  at 
the  right  hand  side,  which  indicates  the  dis- 
tance of  the  tube  from  the  plate.  Tracing  this 
diagonal  line  towards  the  center  of  the  x-ray 
tube  it  is  found  that  a  2;-2  inch  diaphragm  should 
be  used  having  the  tube  at  a  distance  of  2-  inches 
from  the  plate;  also  that  a  31/3  inch  diaphragm 
could  be  used  19  inches  from  the  plate,  or  if  no 
diaphragm  is  used  and  there  is  a  \V2  inch  open- 
ing below  the  tube,  the  tube  may  be  brought 
to  within  15  inches  of  the  plate.  Alany  oper- 
ators do  not  care  to  expose  the  entire  plate, 
utilizing  the  surface  covered  hy  a  circle,  the 
diameter  of  which  is  equal  to  the  width  of  the 
plate. 

zone  around  the  focal  spot  reaching  this  given 
area  will  vary  inversely  as  the  square  of  the 
distance. 


CHAPTER  XVII 

STANDARD    POSITIONS 

The  Arrangement  of  Various  Portions  of 

THE  Body  for  Examination 

General  Considerations 

In  the  determination  of  the  relationship 
between  the  central  ray  and  the  part  to  be 
radiographed,  there  are  two  desiderata. 


Fig.   201. — Iininobilizing  apparatus    for   lateral   view 
of  forehand.     The  hand  grasps  the  wooden  pin. 

1.  The  clear  outlining  of  the  joint  spaces, 
not  overlapped  by  bony  parts. 

2.  Such  a  shadow  of  the  parts  as  shows 
them   in  their   normal   anatomic   relationship. 

Having  determined,  therefore,  the  struc- 
tures to  be  delineated,  it  is  necessary  to  place 
the  part  in  a  certain  posture,  to  properly  im- 
mobilize it  and  to  place  the  tube  in  a  certain 
position  in  relation  to  the  part.  The  consid- 
eration of  the  technique  of  arrangements  of 
parts  for  examination,  will  be,  therefore,  con- 
sidered under  the  following  headings  : 


Fig.  202. — ImmobiHzing  apparatus  for  leg.     The  foot 
is  tied  to  the  upright. 


1.  Essential  features. 

2.  Exposures  or  views. 


3.  Posture. 

4.  Immobilization. 

5.  Tube  position. 


Fig.  203. — Immobilizing  apparatus  over  which  the 
bended  knees  are  placed  to  obtain  complete 
approximation  of  the  lumbar  region  to  plate 
as   in  kidney   examinations. 

In  order  to  avoid  confusion  a  lead  marker 
is  placed  on  the  plate,  indicating  whether  the 
right  or  left  side  is  exposed,  and  a  lead  num- 
ber for  identification  of  the  plate.  These 
should  be  carefully  placed  so  as  not  to  obscure 
the  part  radiographed  and  fixed  to  the  plate 
with  adhesive  plaster  to  avoid  displacement 
during  manipulations. 


Fig.  204. — For  lateral  view  of  the  inner  aspects  of 
the  extremities — the  part  to  be  radiographed 
lies  on  the  horizontal  part  of  the  apparatus  and 
the  other  limb  under  it.     (Gocht.) 

The  difficulties  in  plate  reading  demand  as 
much  information  as  can  be  obtained  in  a 
given  case.  It  is  conducive  to  accurate  read- 
ing, if  more  rather  than  fewer  exposures  are 
made  of  the  part  under  consideration. 

Where  epiphyseal  ossification  is  incom- 
plete, or  where  postural  deformity  is  such  as 
to  give  rise  to  great  distortion,  a  comparative 
exposure  of  the  opposite  side  becomes  neces- 
sary. Certain  examinations,  as  of  chest,  urin- 
ary tract,  and  pelvis,  always  include  both  sides. 


[147] 


Standard  Positions 


Fig.  205 


Fig.  206 


HEAD 

Essential  Features 
Skull 

\'ascular  grooves 
Sutures 

Orbital  boundaries 
Sella  turcica 
Sphenoidal  sinuses 
^lastoid  process. 
Facial  Bones 
Frontal  sinuses 
Ethmoid  sinuses 
^Maxillary  sinuses 
Tempro-maxillary  articulation. 

The    examination    of    the    head   may    be 
made  in  the  following  positions: 

EXPOSURES 
Centric: 

Sagittal 

1.  Ant.  Post.    (Occiput  and  base) 

2.  Post.  Ant.  (Sinuses  and  teeth) 

Horisontal 

3.  Infero-superior    (Base    of    skull,    sphe- 
noidal sinus) 

4.  Supero-inferior   (Sphenoidal  Sinus) 

Frontal 

5.  Sinestro-dextral  ( Sinuses  | 

6.  Dextro-sinestral]  Sella  turcica  j 

Oblique 

7.  Post.  Ant.  (Optic  foramen — orbit) 

Excentric : 

Sagittal 

8.  Post.  Ant.   (Sinuses) 

9.  Infero-superior   oblique    (Os   petrosum) 

Frontal 

10.  Sup.  Inf.  (Mastoid— Jaws) 

Difficulties 
1.  Immobilization.  To  accomplish  this 
various  immobilizing  apparatus  have  been  de- 
vised. One  form  consists  of  a  platform  having 
two  padded  clamps.  Another  form  is  a  canvas 
sling,  in  which  the  head  rests,  the  body  being 


[1481 


HEAD 


149 


in  the  supine  position,  the  tube  below,  the 
plate  above.  The  examination  may  also  be 
made  in  the  sitting  position.  An  apparatus 
for  this  purpose  consists  of  a  framework  hold- 
ing a  swivelled  iron  frame,  8x10  inches,  cov- 
ered with  a  celluloid  window,  against  which 
the  plate  is  placed.  The  plate  in  its  holder 
may  be  adjusted  to  any  angle  to  the  head, 
which  is  immobilized  by  side  clamps  and  a 
chin  rest.  Indicators  at  the  clamps  give  the 
base  lines  and  angles  of  ray.  The  patient  sits 
in  a  chair  beside  the  apparatus  wdiich  may 
be  raised  to  any  height.     (Figs.  207,  208.) 

2.  The  variation  in  the  thickness  of  bones 
and  also  of  skull  diameters  results  in  uneven 
exposure  of  various  parts  and  makes  approxi- 
mation to  plate  difficult. 

3.  Secondarv  radiations  from  brain  tend  to 
fog  bone  detail,  hence  the  use  of  a  small  dia- 
phragm and  long  cylinder  is  necessary. 

4.  In  the  sagittal  view  the  orbital  plate  of 
the  frontal  shadow  falls  over  the  frontal 
sinuses,  the  petrous  portion  of  temporal  over 
the  ethmoid  and  the  basilar  portion  of  the 
occipital  covers  the  maxillary  sinuses.  An  ex- 
centric  exposure  with  the  central  ray  at  a 
definite  angle  to  the  recording  surface  is  neces- 
sary that  this  overlapping  may  be  avoided.  By 
the  proper  arrangement,  the  petrous  bone 
shadow  will  fall  over  that  of  the  lower  part 
of  the  orbit,  leaving  the  antrum  and  ethmoids 
clearly  outlined. 

5.  To  obtain  information  regarding  size  and 
shape  of  structures  of  the  skull,  it  is  important 
that  the  head  be  maintained  in  a  position  with 
its  frontal  plane  absolutely  horizontal  or  ver- 
tical, depending  on  the  method  of  examination. 
Various  levelling  devices  may  be  utilized  to 
do  this.  (Fig.  221.)  It  is  only  thus  that  the 
desired  accurate  overlapping  in  the  lateral 
aspect  is  obtained. 

The  floor  of  the  frontal  sinus,  the  sphe- 
noidal sinus,  the  apex  of  the  petrous  portion 
of  the  temporal,  the  glenoid  cavity,  the  ex- 
ternal auditory  meatus,  the  jugular  foramen. 
and  the  base  of  the  mastoid  process,  all  lie  on 
a  line  drawn  from  the  nasion  through  the 
external  auditory  meatus.  This  line  has  been 
called  the  radiographic  base  line  by  Salmond. 
Three  perjjendiculars  are  erected  on  this  line, 
at   one-third  to  two-thirds  and   one-half   dis- 


FiG.  207. 


Figs.      207-208. — Head      immobilization 
(.Percy  Brown.) 


apparatus.. 


150 


HEAD 


Fig.  2og. — Oblique  view  of  head  leveler,  showing  all 
the  various  parts,  and  rotating  level  on  the  top. 
It  consists  primarily  of  two  parallel  bars  of 
aluminum.  20  cm.  long,  2  cm.  wide,  and  2.5  mm. 
thick.  "  These  bars  are  connected  b}'  two  tele- 
scopic tubes,  the  smaller  one  being  2  cm.  in 
diameter,  and  slides  inside  the  other.  These 
are  controlled  by  an  adjustable  thumb  screw. 
They  are  kept  parallel  and  prevented  from  rotat- 
ing by  a  groove  and  pin.  Upon  the  outer  tube 
is  attached  a  spirit  level  which  is  fixed  exactly 
perpendicular  to  the  plane  of  the  two  parallel 
bars.  To  the  top  parallel  bar  is  attached  another 
spirit  level.  This  spirit  level  above  is  on  a 
pivot  to  permit  its  use  in  two  different  positions. 
This  upper  spirit  level  is  rotated  to  the  proper 
angle,  which  is  controlled  in  each  instance  by 
a  "  pin."     (  Pf abler  ). 


Fig.  210 


tance  from  either  end,  dividing  the  head  into 
four  areas. 

Region  A  contains  the  air  sinuses  witheihe 
exception  of  the  sphenoid  and  the  facial  bones. 

Region  B  contains  the  sphenoidal  sinus  and 
sella  turcica  and  ascending  ramus  of  jaw. 

Region  C  contains  mastoid  and  petrous  por- 
tions of  temporal. 

Region  D  contains  the  lateral  sinus  and 
basilar  portion  of  occipital. 

To  radiograph  any  of  these  areas  the  central 
ray  must  be  passed  through  the  center  of  the 
particular  area  and  its  base  line. 

EXPOSURES 
la.  Antero-Posterior  (general). 
Essential  Features 

Bone  detail  of  occipital  region  with  lamb- 
doid  suture  above,  foramen  magnum  be- 
low, and  mastoids  laterally. 

Posture  (Fig.  210). 

Occiput  to  plate,  by  elevation  of  head 
Chin  tilted   down,   canthus — auricular   line, 

vertical 
Plate  (8x  10)  upper  edge  one  and  one-half 

inches  above  crown 

Immobilization 

Clamps  to  side  of  head 

\\'eighted  canvas  band  over  forehead 

Tube  Position 

Lower  edge  of  five  inch  cone  at  supraorbital 

ridge,  tilt  downward  20° 
Elevate  one  inch  from  skin 
Central  ray  just  above  and  between  frontal 
eminences 

lb.  Antero-Posterior  (for  Antero-Posterior 
\^iew  of  Mastoid  Process) 

Posture 

Occiput  to  plate 

Immobilization 

Band  over  forehead,  clamps  to  side 

Tube  Position 

Small  cylinder  tilted  five  degrees  inward 
Central  ray  through  tip  of  mastoid 


HEAD 


151 


2a.  Postero-Anterior 
(For  maxillary  sinuses  and  incisor  teeth) 

Posture  (Fig.  211) 

Chin  to  plate 

Nose  1  to  1.5  cm.  from  plate. 


Immobilization 

Clamps  to  side  of  head 
Pressure  of  cone  above 


Tube  Position 

Central  ray  through  base  of  nose,  perpen- 
dicular to  recording  surface 
Long  axis  of  tube  parallel  to  plate 
Five  inch  cone,  2  inch  from  head 

2b.   Postero-Anterior    (for    frontal    bone.) 
Posture 

Nose  and  forehead  to  plate  which  is  placed 
horizontally.  A  line  through  glabella  and 
symphysis  of  jaw  should  be  horizontal. 

Immobilization 

As  above 


Fig.  211. — Position  for  maxillary  sinuses  and  incisor 
teeth.     (Waters    and    Waldron). 


Tube  Position 

Central  ray  two  inches  below  occipital  pro- 
tuberance 


3.  Infero-Superior 
(For  sphenoidal  sinuses  and  base  of  skull) 
(Structures  of  mouth — salivary  calculus) 

Posture     (Figs.  212,  213) 

Patient  supine,  head  hangs  over  edge  of 
table  until  Reid's  line  is  horizontal.  Five 
inch  cone.  Edge  at  symphysis  of  jaw.  In- 
cline five  degrees  toward  chin.  Plate  at 
vertex.  For  salivary  calculus,  film  hor- 
izontally in  mouth.  Intensifying  screen 
may  be  necessary. 

Immobilization 

Weighted  band  over  forehead 

Tube  Position 

Five  inch  cone,  directed  under  chin,  towards 
base 


Fig.  212 


152 


HEAD 


Fig.  213, — Radiograph.     Infero-superior  view. 


4.  Supero-Inferior 

(Sphenoidal  Sinus  and  Septum) 

Posture 

Patient   in   chair,    head   bent   slightly   back- 
ward 
Head  vertically  immobilized 

a)  Film  horizontally  in  mouth 

b)  Film   in   naso-pharynx,    in   contact   with 

pharyngeal  arch 

c)  Plate  under  chin 


Immobilization 

Special  holder  for  film 

No  swallowing 

Fixation  of  head 

Cocainization  of  phar3mx  ma)'  be  necessary 


Tube  Position 

At  vertex.  Central  ray,  two  centimeters 
anterior  to  plane  through  external  audi- 
tory meatus. 


Fig.  214 


5.  Sinestro-Dextral 
6.  Dextro-Sinestral     (Fig.  214) 

Posture 

Trunk  prone  or  on  side 

Head  on  side — lower  jaw  parallel  to  lower 

edge  of  plate 
Frontal  plane  parallel  to  recording  surface 
Head  to  be  levelled, — very  important 

Immobilization 

Clamp  to  forehead  and  occiput,  band  over 
head 

Tube  Position 

a)  For  sella  turcica,  centering  point  one 
and  one-half  inches  in  front  of  external 
auditory  meatus,  on  a  line  from  upper 
margin  of  orbit  to  external  auditory 
meatus. 

b)  To  obtain  lateral  view  of  sinuses,  cen- 
tering point  over  outer  canthus. 

When    stereoscopic    plates    are    made,    the 
shifting  should  be  from  above  downward. 


HEAD 


153 


7.  Oblique  Postero-Axterior 

(Sphenoidal  sinuses,  optic  foramen,  orbit.) 

Posture    (Fig.   215) 

Orbit  to  plate 

Head  turned  forty-five  degrees 

Immobilization 

As  above 
Tube  Position 

Central  ray  two  inches  behind  and  one  and 
one-half  inches  above  opposite  external 
auditory  meatus,  through  center  of  orbit 
to  plate 


Fig.  215 
I — root  of  frontal  sinus  3 — posterior  ethmoid 

2 — anterior  ethmoid  4 — sphenoid 


8.    SUPERIOR-IXFERIOR     SaGITTAL     ExCEXTRIC 

(Frontal,  ethmoid  and  maxillary  sinuses) 

Posture  (Fig.  216) 

Forehead  to  plate  on  incline  block  23  de- 
grees to  horizontal 

Immobilization 

Clamps — three  inch  cone  pressed  directly 
o\'er  occiput 

Tube  Position 

Central  ray  perpendicular  to  horizontal 
])lane,  passing  through  glabella.  In 
other  words,  central  ra}'  to  pass  through 
head  at  angle  of  twenty-three  degrees  to 
line  extending  from  external  auditory 
meatus  to  glabella 


Fig.  216. — Law  utihzes  a  20  degree  angular  block 
and  place-,  the  tip  of  an  angle  finder  opposite 
the  glabella,  the  left  arm  passing  across  the  ex- 
ternal auditory  meatu>.  the  right  arm  extending 
alongside  the  cone  and  giving  the  direction  of 
the  central  ray.  This  is  the  Caldwell  position. 
The  angle  between  the  two  arms  is  2}°^ 


154 


HEAD 


Fig.  217 


Fig.  2i8  Fig.  219 

Figs.  217,  218,  219. — Position  of  head   for  outlining 
internal   ear.        (Stuvers). 


9.  Infero-Superior  Oblique 

(Petrous  portion  of  Temporal) 

(Internal  Ear)  ^^ 

Essential  Features 

Internal  auditory  meatus 

Semicircular  canals 

Vestibulae 

Cochlea 

Tympanum 

The  petrous  bone  is  projected  in  the  squa- 
mous portion  of  the  temporal  bone.  To  avoid 
tlie  projection  of  middle  ear  structures  over 
the  ductus  semicircularis,  the  central  ray  is 
passed  to  the  side  of  the  median  line. 


Posture 

Trunk  prone 
Orbit  to  plate- 


degrees. 


-sagittal  plane  at  angle  of  45 


(Figs.  217,  218,  219). 


Immobilization 

Clamps — cones — three  inch  cylinder 

Tube  Position 

Central  ray  through  occipital  protuberance 
but  inclined  twelve  degrees  cephalwards 
Tube  plate  distance  to  be  increased  be- 
cause of  distance  of  petrosa  from  plate. 
Use  intensifvinff  screen 


10.  Superior  Inferior  Frontal  Excentric 

(Mastoid  portion  of  Temporal) 

Essential  Features 

The  condyloid  process  of  lower  jaw 
External  and  internal  auditory  meatus,  over- 
lapping 
Mastoid  cells 
Lateral  sinus 

Posture  (Fig.  220). 

Side   of    head   to    incline-block    15    degrees 
Pinna  pulled  forward 

Reid's  base  line  parallel  to  upper  edge  of 
plate 

Immobilization,    Band,    Clamps   or   Cylinder 

Tube  Position 

Three  inch  cone.  Lower  edge  one  inch 
above  external  auditory  meatus ;  front 
edffe  tangent  to  meatus 


TEETH 


155 


MAXILLAE  AND  TEETH 

The  examination  of  the  maxillae  and  teeth 
ma\-  lie  made  bv  the  intraoral  and  extraoral 
methods.  In  the  former,  the  recording  sur- 
face (film)  is  placed  within  the  mouth,  in  the 
latter  (film  or  plate)  is  placed  on  the  exterior. 
The  extraoral  method  is  of  greater  general 
utility,  for  the  intraoral  method  permits  only 
the  study  of  the  teeth  and  its  immediate 
alveolar  process.  Both  methods  are  essential 
in  the  study  of  a  case. 

INTRAORAL 

Gener.\l  Considerations 

The  aim  is  to  obtain  a  shadow  of  the  teeth 
which  conforms  as  closely  as  possible  to  the 
diameters  of  the  tooth  itself.  To  this  end 
the  central  ray  should  strike  the  tooth  at  a 
certain  angle  and  the  film  be  disposed  to  the 
alveolar  process  in  certain  relationship. 

Posture 

The  examination  may  be  made  in  the  hori- 
zontal or  sitting  posture.  The  former  is 
preferable,  since  it  is  more  conducive  to 
complete  immobilization,  ^^'hen  made 
in  the  sitting  posture,  a  dental  chair  or 
an  ordinary  chair  fitted  with  head  rest  and 
clamps  may  be  used.  The  dental  chair 
should  be  provided  with  every  range  of 
movement  and  adjustment  and  with  a 
head  rest  which  is  detachable  and  adjust- 
able. The  head  is  placed  in  the  proper  po- 
sition for  examination  b_v  reference  to 
three  base  lines  (Fig.  221).  1.  The  in- 
fraorbital auricular  line  is  one  which  ex- 
tends frpm  the  lower  border  of  the  orbit 
to  the  external  auditory  meatus.  In  ex- 
aminations of  the  teeth  of  the  upper  jaw 
and  in  the  molar  teeth  of  the  lower  jaw 
in  the  vertical  posture,  this  line  must  be 
horizontal.  2.  The  labial  auricular  line 
is  one  which  extends  from  the  angle  of 
the  mouth  to  the  external  auditory 
meatus.  In  the  examination  of  the  teeth 
of  the  lower  jaw  in  the  vertical  postiu-e 
this  line  must  be  horizontal.  3.  The  su- 
l)raorbital    auricular    line.      This    should 


k 


Fig.  221. — Base  lines. 


•^^S|^"Oj^ 

^^^^£^HL     "3^^^^^  ..m^^*- 

i. 

^HBAJ^AI^ 

i 

h 

^^■hH^^p    ^  If 

« 

:>'-li 

^' 

V 

-^ 

- 

^^Ujkj:^^. 

\  ^V^^^^^^H^K^^ 

i 

'''K 
•^ 

^ 

5 

i^ 

H 

Fig    223 


156 


TEETH 


P  F 

Fig.   223. — Direction    of    central    ray. 
placed   horizontally. 


TF    for    film 


be  with  the  body  in  the  horizontal  posture, 
vertical  in  the  examination  of  the  lower 
jaw  with  the  horizontal  film  for  the 
receding  type  of  lower  jaw.  In  the 
protruding  type  of  lower  jaw,  the  infra- 
orbital auricular  line  is  vertical.  The 
head  is  varied  as  regards  its  position, 
depending  on  the  particular  teeth  to 
be  examined.  For  the  lateral  incisors, 
canine  and  bicuspid  the  head  is  turned  at 
an  angle  of  forty-five  degrees,  for  the 
molar  teeth  the  head  is  turned  in  com- 
plete lateral  posture. 

Immobilization 

The  head  must  be  immobilized  by  clamps, 
assisted  by  voluntary  eiifort  of  the  patient. 
The  film  is  immobilized  by  the  finger  of 
the  patient,  the  right  hand  being  used  for 
the  left  upper  and  lower  jaws.  The  lia- 
bility of  slipping,  either  on  the  gum  or 
under  the  patient's  fingers,  due  to  moisture 
of  the  paraffined  paper,  may  be  obviated 
by  wrapping  the  package  in  white  tissue 
or  parchment  paper.  The  difficulty  of 
obtaining  complete  fixation  of  the  film 
by  the  hand  has  resulted  in  the  produc- 
tion of  numerous  devices  for  holding  the 
film  in  place  mechanically. 


Tube  Position 

The  tube  stand  should  be  capable  of  adjust- 
ment in  all  directions,  should  be  suitably 
marked  so  as  to  permit  the  determination 
of  the  angle  of  inclination.  The  path  of 
the  central  ray  should  be  indicated  in  the 
diaphragm  of  the  tube  stand.  The  sim- 
plest way  to  do  this  is  to  insert  a  piece 
of  cardboard  to  which  a  straw  has  been 
fixed,  in  the  diaphragm  opening  of  the 
tube  carried,  having  previously  adjusted 
the  tube  so  that  the  central  ray  goes 
directly  through  the  center  of  the  dia- 
phragm. 

The  central  ray  is  directed  perpendicularly 
to  the  line  in  the  midangle  between  that 
of  the  tooth  and  the  film  and  directed 
through  the  apex  of  the  particular  tooth 
and  at  right  angles  to  the  broad  axis. 
(Fig.  224.)  The  central  ray  must,  there- 
fore, bear  a  definite  relationship  to 

1.  The  long  axis  of  the  tooth. 

2.  The  apex  of  the  tooth. 

3.  The    tangential    line    of    the    broad   axis 

of  the  tooth. 


TEETH 


157 


1.  The  Long  Axis. 

The  tube  position  is  such  that  the  central 
ray  is  more  or  less  at  an  angle  to  the 
film,  the  variation  of  the  angle  depending 
on  the  particular  teeth  radiographed  and 
the  position  of  the  film,  whether  placed 
directly  against  the  gum,  or  horizontally 
between  the  teeth.  Thus  for  the  lower 
molars  the  film,  when  placed  behind 
the  teeth,  is  nearly  parallel  to  their  axes, 
consequently  the  central  ray  may  be 
directed  almost  perpendicularly  to  the 
film.  On  the  other  hand,  if  the  upper 
central  incisors  are  to  be  examined,  the 
film,  when  placed  behind  these  teeth,  is 
at  an  angle  to  their  axes  and  the  central 
ray  can  no  longer  be  directed  at  right 
angles  to  the  film  but  at  a  certain  obliqui- 
ty. Because  the  lengths  of  the  roots 
diflfer  and  the  planes  of  the  buccal  and 
lingual  roots  are  at  dififerent  angles,  it  is 
impossible  to  obtain  true  shadows  of  both 
with  the  same  exposure.  In  a  general 
view  a  plane  midway  between  both  is 
utilized.  The  lower  central  teeth,  because 
of  the  slight  obliquity  of  their  apices  and 
the  slight  backward  curving  of  the  film, 
necessitate  the  directing  of  the  central 
ray  upward  at  a  slight  angle.  When  the 
film  is  placed  horizontally  between  the 
teeth,  the  angle  at  which  the  central  ray 
strikes  the  tooth  is  greatest  and  should  be 
such  as  gives  a  shadow  of  the  tooth 
which  conforms  in  its  diameters  to  the 
tooth  itself.  This  angle  is  one  which 
passes  the  central  ray  at  right  angles  to 
a  line  in  the  midangle  between  that  of  the 
tooth  and  the  horizontal  film.  (Fig. 
223).  This  latter  method  has  only  a 
limited  applicability  and  will  be  discussed 
in  detail  later. 

2.  The  Apices. 

The  apices  of  the  upper  teeth  are  about  one 
centimeter  below  the  lower  margin  of  the 
orbit,  the  canines  reaching  higher  than  the 
others.  The  apices  of  the  lower  teeth  are 
about  one  centimeter  above  the  lower 
border  of  the  alveolar  process. 

3.  The  Broad  Axis. 

The  importance  of  the  maintenance  of  the 
perpendicular  relationshii)  of  the  central 
ray  to  the  tangential  line,  parallel  to  the 
broad  axis  of  the  teeth  lies  in  the  avoid- 
ance of  distortion  in  the  broad  axis  and 


overlapping  of  shadows.  No  more  than 
three  teeth  can  be  correctly  radiographed 
on  one  film. 

The  target  skin  distance  need  not  exceed 
fourteen  inches.  The  actual  length  of  the 
tooth  may  be  determined  by  the  insertion  of  a 
known  length  of  wire  into  the  tooth  and  a 
normal  radiograph  made.  Thus  the  length 
of  the  shadow  of  a  known  length  of  wire  is 
to  the  length  of  the  wire,  as  the  length  of  the 
shadow  of  the  particular  tooth  is  to  the  length 
of  the  tooth  itself.  It  has  been  estimated  that 
at  fourteen  inches  target  film  distance,  the 
exposure  being  in  all  respects  a  normal  one, 
the  enlargement  of  the  shadow  of  the  tooth 
is  negligible,  and  the  size  of  the  tooth  may  be 
determined  by  the  measurement  of  the 
shadow.  The  shadow  of  an  abscess  or  cyst 
will  nearly  always  be  either  slightly  larger  or 
smaller  than  the  tooth  itself,  depending  upon 
whether  it  is  anterior  or  posterior  to  the 
root.  As  a  rule  the  lesions  appear  in  the 
radiograph  to  be  smaller  than  they  actually 
are  in  proportion  to  the  size  of  the  root. 

Ten  films  are  necessary  to  completely  ex- 
amine the  mouth. 

Upper  Jaw: 

1.  Right  molars 

2.  Bicuspids  and  canine 

3.  Incisors 

4.  Left  bicuspids  and  canine 

5.  Left  molars 

Lower   Jaw : 

6.  Right  molars 

7.  Right   bicuspids  and  canine 

8.  Incisors 

9.  Left  canine  and  bicuspids 
10.  Left  molars 

A  convenient  method  of  marking  the  films 
is  to  perforate  them  after  exposure  and  before 
development  by  a  needle  puncture  through 
paper  and  film.  Thus  film  No.  1,  as  above 
with  one  perforation,  two  with  two  and  so 
on  till  five  for  the  left  upjier  molar.  The 
lower  films  are  similarly  marked  with  the  addi- 
tion of  an  extra  perforation  below  the  others 
to   indicate   the   lower  jaw. 


158 


TEETH 


Lower  Jaw  (Fig.  225) 
Articular  Labial  Line — Horizontal 


FILM 

HEAD 

CENTRAL   RAY 
Angle  below  base  line 

1. 

Incisors 

Sagittal 
position 

10° 

2- 

Canines 

Oblique  45° 
to  R.  or  L. 

10° 

3. 

Bicuspids 

Oblique  45° 
toR. 

10° 

4. 

Molars 

Lateral  90° 
to  R.  or  L. 

Central  ray   parallel 

to  base  line 
Perpendicular  to  film 

Note — Because  of  different  inclination  of  roots 
of  the  molar  teeth,  films  may  be  made  as  follows : 

1.  General  view   (both  roots)   buccal   roots 

lengthened  and  projected  into  antrum 
Lingual  roots  shortened 

2.  View  of  buccal  roots 
Lingual  root  elongated 

3.  View  of  lingual  roots 
Buccal  roots  shortened 

The  relationship  of  the  molar  roots  to  the  antrum 
should  be  judged  by  the  relative  position  of  the 
apices  of  buccal  roots. 


Fig. 


'J'EETH 


159 


Upper  Jaw  (Fig.  226) 
Infra-Orbital  Auricular   Line — Horizontal 


FILM 

HEAD 

CENTRAL  RAY 

Angle  above  base  line 

1. 

Incisors 

Sagittal 

Flat  palate  50 
Average  "     45 
High       "    40 

2. 

Canines 

45°  oblique 

Flat  palate  55 
Average  "    50 
High       "    45 

3. 

Bicuspids 

45°  oblique 

Flat  palate  55 
Average  "    50 
High        "    45 

4. 

Molars 

90°  lateral 

Flat  palate  45 
Average  "    40 

Fig.  226 


160 


TEETH 


Film  Horizontally  Placed  (Fig.  227) 
Upper  Jaiv 

Posture 

Head  vertical 

Infra-orbital  auricular  orbital  line  horizontal 

Tube  Position 

Central  beam  sixty-five  degrees  (with  re- 
ceding forehead)  to  base  line  through 
apices  of  roots  of  teeth.  For  protruding 
forehead — seventy-five  degrees 

Lower  Jaw 
(For  protruding  lower  jaw^ 

Posture — horizontal 

Infra-orbital  auricular  line  vertical 

Tube  Position 

Central  beam  fifteen  degrees  below  hori- 
zontal 

(For  retracted  lower  jaw) 

Posture — horizontal 

Supra-orbital  auricular  line  vertical 

Tube  Position 

Central  beam  fifteen  degrees  below  hori- 
zon':al 


Fig.  227 


TEETH  EXTRAORAL 


161 


EXTRAOKAL    MeTHOD 

Because  of  the  overlapping  of  bony  parts, 
spine,  occiput  and  opposite  side  of  jaw,  it 
becomes  necessary  to  examine  the  various  por- 
tions of  the  alveolar  processes  in  certain  pos- 
tures and  with  a  certain  definite  relationship 
between    central    ray    and    recording    surface. 

Essential   Features 

The  entire  alveolar  region  of  the  jaws  from 
the  incisor  teeth  anteriorly  to  the  angle  of  the 
jaw  posteriorly  and  from  the  floor  of  the  orbit 
to  the  inferior  margin  of  the  mandible.  These 
conditions  cannot  be  attained  by  one  view. 

Posture     (Fig.  229) 

The  sitting  or  prone  posture  may  be  utilized. 
The  plate  holder  should  be  movable  in  all 
directions  and  a  scale  should  be  attached 
so  that  the  angle  to  the  horizontal  can  be 
determined,  and  permit  the  centering  of 
the  tube  on  it.  All  metal  parts  capable 
of  removal  from  within  the  mouth  or  in 
ears  or  hair  should  be  removed.  A  cork 
is  placed  between  the  teeth  so  as  to  keep 
mouth  open. 

Immobilization 

Clamps  may  be  applied  to  the  anterior  and 
posterior  parts  of  the  skull  and  to  the 
lateral  parietal-temporal  region 

Tube  Position 

The  central  ray  is  directed  below  the 
jaw  at  an  angle  of  60°,  70  ~  or  90°  to  the 
plate.     Target  plate  distance  18  inches. 

Lower  ]\Iolar  Region 

Lateral  Viezv 

Posture     (Figs.  228e.  229) 

Head  lateral  resting  on  zygoma 
Chin  away   from  plate 
Sagittal   plane   horizontal 
Cork  between  incisor  teeth. 

Tube  Position 

Central  ray  directed  lo  molar  region 
through  the  second  molar  at  an  angle  of 
60°  to  65?  from  the  horizontal. 


Fig.  228. — Extra-oral   method. 


Fig.  220 


162 


TEETH  EXTRAORAL 


Fig.  229a. 


Bicuspids  and   Molars  Upper  and  Lower 

Essential  Features 

The  plate  should  include  the  structures 
from  the  lateral  incisors  to  the  second 
molars.  To  show  all  molars  arrange  as 
per  Fig.  228d.  Sagittal  plane  15-  to 
horizontal. 

Posture     (Fig.  228c;) 

The  head  is  placed  against  the  plate  resting 
on  malar  prominence.  Sagittal  plane  30^ 
to  horizontal. 

Cork  between   incisor  teeth. 

Tube  Position 

The  central  ray  is  directed  at  an  angle  of 
seventy  degrees  to  the  plate  and  10'  for- 
ward directed  through  last  molar  tooth. 

Lateral   Incisors,    Canine   and   Bicuspids 

Essential  Features 

The   plate   should   show   the   central   upper 

and  lower  incisors,  the  anterior  portions 

of  the  mandible  maxilla,  and  the  mastoid 

process  posteriorly. 

Posture     (Figs.  228b,  229a) 

Body  prone,  head  resting  on  orbit,  nose  and 
chin  to  plate.  Sagittal  plane  65°  to 
horizontal.      Cork  between   incisor  teeth. 

Tube  Position 

Central  ray  seventy  degrees  to  recording 
surface,  through  opposite  incisor. 

Central  Incisor  Region 


Posture 

Nose  and  chin  to  plate, 
to  horizontal 


Sagittal  plane  90° 


*FiG.  22gb. — Instead  of  giving  the  central  ray  an  in- 
clination of  sixty  degrees,  the  head  may  be 
placed  on  a  thirty-degree  incline  from  the  hori- 
zontal. 


Tube  position 

Central  ray  through  point  below  occipital 
protuberance,  70  degrees  to  plate 

Stereoscopic  examination  by  the  extraoral 
method  may  be  made  by  the  use  of  a  tunnelled 
incline. 

The  technique  consists  in,  first,  making  an 
exposure,  second,  changing  the  exposed  plate 
for  a  second  plate,  moving  the  tube  two  and 
one-half  inches  and  making  the  second  ex- 
posure. The  long  edge  of  the  plate  should 
be  parallel  to  the  long  supporting  bars  of  the 
stand. 


*  The  diagrams  illustrating  the  radiography  of 
the  teeth  have  been  modified  from  those  by  Cies- 
Z3'nski. 


SPINE 


163, 


SPINE 

In  the  examination  of  the  spine  the  tech- 
nical rules  pp.  143,  144.  must  be  noted.  Par- 
ticularly- so  in  the  examination  of  the  cervical 
spine,  because  of  the  narrowness  of  the  inter- 
vertebral joint  spaces  and  the  peculiarity  of 
the  articulations. 

Fixation,  immobilization  and  the  use  of 
the  cylinder  are  essential  to  minimize  in- 
voluntary and  voluntary  movements,  particu- 
larly in  the  examination  of  the  head  and  neck. 

Essential  Features   (Fig.  230) 

.1.  Bone  details  in  bodies 

2.  Upper  and  lower  articular  process 

3.  Spinous   process 

4.  Transverse  processes 

5.  Intervertebral  spaces 

Exposures 

1.  Ventro-dorsal 

2.  Dorso-ventral 

3.  Sinestro-dextral 

4.  Dextro-sinestral 

5.  Obliques 

Difficulties 
A.    Cervical 

1.  The  frontal  curve  of  the 
close  approximation  to  plate, 
overcome  by  the  use  of  the  incline  block. 

2.  The  occiput  covers  the  first  and  second 
cervical  vertebrae  in  lateral  view.  The  chin 
should,  therefore,  be  depressed. 

3.  The  lower  jaw  covers  the  first  and  second 
vertebrae  in  the  ventro-dorsal  view,  hence  ele- 
vate chin  and  incline  tube. 

4.  The  shoulder  covers  seventh  cervical  in 
lateral  view,  hence  elevate  shoulder  or  ex- 
amine in  the  lateral  position. 

B.    Dorsal 

1.  Median  shadow  covers  dorsal  spine  in 
sagittal  view.  Examine  in  the  ventro-dorsa! 
oblique. 

2.  Liver  covers  the  tenth,  eleventh  and 
twelfth  vertebrae.  Examine  as  for  kidney,  in- 
cline tube  from  below  upward. 

C.    Luiiibar 

1.  Normal  frontal  curve  prevents  close  ap- 
proximation of  spine  to  plate,  hence  flex 
thighs,  elevate  shoulders. 

2.  Gastro-intestinal  contents  obscure  lumbar 
spine,  hence  the  necessity  of  thorough  purga- 
tion. 

3.  Lumbo-sacral  segment  lies  in  ditiferent 
axis  from  lumbar  spine,  therefore,  change  axis 
of  central  rav. 


spine  prevents 
This   may  be 


Jst  cenncal 
or  Atlaa. 

Znd  cervical '  li.^,^  jk 

or  Axis,   rfn?^^-: 


Fig.  230, —  1  lie  arrow 
indicate  the  vertebrae 
lusually  obtained  in  ex- 
posures of  the  cervical, 
dorsal  and  lumbar  verte- 
brae on  single  plates. 


164 


CERVICAL  SPINE 


Technical  Difficulties 

1.  Rays  of  great  penetration  are  necessary 
and  the  resulting  scattered  and  secondary 
radiations  require  careful  diaphragming  and 
the  use  of  cones. 

2.  Distortion  resulting  from  distance  of 
part  from  plate,  particularly  in  the  oblique 
demands  increased  tube-plate  distance  with 
resulting  increase  of  exposure. 

UPPER   CERVICAL   VERTEBRAE 

(  occipto-atlanto-axial  articulation  ) 
Essential  Features 

Occipital  fossa 

Axis 

Atlas  with  its  bifurcated  spinous  process 

Odontoid  process 

Exposures 

1.  Ventro-dorsal 

2.  Sinestro-dextral  or  dextro-sinestral 

Ventro-Dorsal 
Posture     (Fig.  230a) 

Occiput  to  plate,  which  extends  from  occi- 
pital protuberance  downward,  chin  ele- 
vated* 

Immobilization 

Clamps  or  bags  to  side  of  head,  slit  strap 
over  chin 

Tube  Position 

Five   inch   cylinder.     Copper   circumference 

resting  on  chin 
Incline    thirty    degrees    upward    in    median 
line 

Dextro-Sinestral 
Sixestro-Dextral 

Posture     (Figs.  231,  231a.) 

Side  of  head  to  plate  to  include  pinna.  Chin 
elevated 

Immobilization 

Strap  over  lower  jaw — cone  in  contact  with 
angle  of  jaw 

Tube  Position 

Cylinder  directed  up  and  back,  central  ray 
through  mastoid 


Fig.  231a 


*  By  placing  cork  between  the  teeth,  the  raj-  may  be 
directed  through  open  mouth  towards  the  base  of 
the  occiput,  the  lower  edge  of  the  upper  incisor  and 
tip   of   mastoid   being   in   same   perpendicular   plane. 


DORSAL  SPINE 


165 


LOWER  CERVICAL  VERTEBRAE 

(3rd  to  7th   inclusive) 
Essential   Features 

1.  Joint  spaces 

2.  Submaxillary  region 

3.  Hyoid  bone  with  its  cornu 

4.  Caracoid  and  thyroid  cartilages 

5.  Tracheal  shadow,  shown  by  virtue  of  its 
air  content. 

Note. — Fractures  are  commonly  associated 
with  dislocations.  These  are  more  frequent  in 
lower  than  in  upper  part  of  cervical  spine. 

Exposures 

1.  Ventro-dorsal 

2.  Dextro-sinestral  and  sinestro-dextral 


Vextro-Dorsal 


Posture 


Occiput  to  plate  on  incline  block  to 
straighten  out  cervical  curve.  Plate  is  to 
e.xtend  below  the  seventh  cervical  spine. 
Head  rotated  laterally 


Tube  Position 

Five  inch  cone. 


Lower  edge  at  mandubruni 


Dextro-Sixestral. 
Sixestro-Dextral 

This  is  also  posture  to  show  hyoid  bone, 
epiglottis,  larynx,  vocal  cords  and  carotid 
arteries 

Posture 

1 )  Head  lateral,  trunk  lateral  or  prone,  chin 
elevated 

2)  Dorsal  decubitus,  plate  to  side  of  neck, 
pressed  into  supra-clavicular  space, 
shoulder  depressed.  Pad  under  base  of 
neck  and  upper  dorsal  region.  Head 
thrown  back,  chin  elevated  (Fig.  233) 

Immobilization 

Sandbags  against  plate 

Tube  Position 

Lower  edge  of  cone  at  shoulder.  Central 
ray  through  4th  cervical,  axis  directed 
downward 

Radiographic  hint ; — avoid  overexposure 


Fig.  232. — Radiograph  lower  cervical  and  upper 
dor.'ial  vertebrae. 


Fig.    233 


Fig.  23.\ 


166 


DORSAL  SPINE 


Fig.  235 


Fig.  235a. — For  entire  dorsal  spine, — the  cone  is 
removed. 


DORSAL  SPIXE 
(1   to    10th   dorsal  inclusive) 
Essential   Features  ** 

1.  Transverse  processes 

2.  Intervertebral  spaces 

3.  Articular  portion  of  ribs 

Exposures 

1.  \'entro-dorsal  excentric 

2.  A'entro-dorsal   oblique 

\'extral  Dorsal  Excextric 
Posture    (^Fig.  235) 
Dorsal  decubitus 

Immobilization 

Cessation   of   breathing   during  exposure 

Tube  Position 

Rectangular  cone  to  the  right  of  sternum. 
Incline  downward  and  to  the  left 

A'extro  Dorsal  First  Oblique 

Posture  (Fig.  271 ;  Fig.  235a) 

Oblique  rotation  of  body  45  degrees  to  hori- 
zontal. Right  shoulder  elevated.  Right 
arm  over  lead.  Left  arm  extended  and 
abducted.     Plate  to  left  chest 

Immobilization 

Sand  bags  under  right  buttock,  right  thigh 
over  left 

Tube  Position 

Tube  at  or  in  front  of  the  axillarv  line 


DORSAL  SPINE 

(11th  to  12th  dorsal) 

Exposure — Vejvtro  Dorsal 

Posture   (  Fig.  279) 

Dorsal  decubitus   ( See  kidney) 

Immobilization 

Compression  with  five  inch  cone  with  loofah 
or  rubber  ball,  cessation  of  breathing 

Tube  Position 

Obliquely  upward  twenty  degrees.  5"  cone 
Upper  edge  cone  below  zyphoid 


LUMBAR  SPINE 


167 


LUMBAR  SPINE 
Essential   Features 

L  Bone  detail  of  lumbar  vertebrae 

2.  Transverse  process 

3.  Spinous  process 

4.  Superior  and  inferior  articular  process 

5.  Intervertebral  spaces* 

6.  Lumbo-sacral  segment 

Note :  The   shadow  of   the  vertebrae   have 
rounded  corners  in  children. 

Exposures 

1.  \'entro-dorsal 

2.  Lateral  (Figs.  237a  238) 

Posture  (Fig.  236) 

Dorsal    decubitus,    knees    flexed,    shoulders 
slightlv  elevated 


Fig.  236 


Immobilization 

Compression  with  cone  and  loofah  sponge 
or  inflated  rubber  ball 


Tube  Position 

General — Rectangular  compression  with 
center  over  umbilicus  and  incline  ten  de- 
grees upward. 

For  1st  and  2nd  lumbar — Upper  edge  of  3" 
cone  at  ensiform  process.  Incline  10 
degrees  upward 

For  2nd  and  3rd  lumbar — Upper  edge  of 
cone  slightly  above  umbilicus  and  perpen- 
dicular 

For  4th  and  5th  lumbar — Middle  of  cone 
level  of  interspinous  line.  Incline  10 
degrees  downward 

The  third  lumbar  spine  is  the  most  common 
seat  of  pathological  processes.  Caution :  ex- 
amine the  transverse  processes  closely.  Frac- 
tures of  them  mav  simulate  calculi 


*  Necessitates  the  examination  of  only  three  bodies 
on  each  plate. 


Fig.  237. — Lower   dor.^al   and   lumbar   spine. 
(Radiograph.) 


168 


SACRUM 


Fig.  237a. — L  equals  centering  point  for  lumbar 
spine.  mid-a.xillar\'  line  at  lower  border  tenth  rib. 
S  equals  centering  point  for  lumbar  sacral  spine, 
one  inch  below  highest  point  of  iliac  crest. 


Fig.  238. — Arrangement  for  lateral  view  of  lumbar 
spine.  The  long  cylinder  is  used  to  minimize 
distortion.  The  c}'linder  is  placed  between  the 
lower  ribs  and  the  crest  of  the  ilium.    (Hickey.) 


.  239. —  (a)  Direction  of 
(b)  Direction  of  axial 
junction. 


axial    ray    for    sacrum, 
rav    for    lumbo-sacral 


LUMBO-SACRAL  SEGMENT 
Essential  Features 

1.  Body  and  transverse  process  of  last 
lumbar 

2.  Lumbo-sacral  space 

Exposures 

1.  Ventro-dorsal 

2.  Oblique 

Ventral  Dorsal 
Posture 

Dorsal,  legs  extended 
Immobilization 

Compression  cone   with  loofah    or    rubber 
ball 
Tube  Position 

Upper  edge  of  five  inch  cone  one  inch  above 
umbilicus,    inclined  ten   degrees   upward. 

Oblique 
Posture 

Trunk  in  first  oblique,  ventro-dorsal 

Immobilization 

Cessation  of   respiration 
Tube  Position 

Five  inch  cone.  Central  ray  through  mid 
point    between    crest    and    umbilicus 

SACRUM  AND  COCCYX 
Essential  Features 

1.  Sacrum.  Upper  surface  of  sacrum  is  2 
inches  below  umbilicus ;  lower  surface  is  at 
level  of  symphasis. 

2.  Sacro-iliac  joints.  The  synchrondases 
extends  from  2)^  to  43/^  inches  below  um- 
bilicus. 

Exposures 

1.  Ventro-dorsal — tube  position  as  above 

2.  For  sacro-iliac  joints  and  iliac  arteries, 
five  inch  cone  on  either  side  of  median  line. 

Difficulties 

1.  Bone  is  thin  and  easily  penetrated  (do 
not  use  too  penetrating  a  ray). 

2.  Rectal   contents   obscure — enema. 

4.  Marked  adiposity — inject  air  in  rectum. 
Posture 

Dorsal — legs  extended 
Immobilization 

Five  inch  compression  cylinder  with  loofah 
inflated  ball 
Tube  Position 

Lower  edge  5"  cone  just  above  symphysis, 
incline  ten  degrees  obliquely  downward, 
central  ray  two  inches  above  symphysis. 
Radiographic  hint ;  use  soft  rays  and 
avoid  overexposure   (Fig.  239) 


PELVIS 


169 


PELVIS    (General) 
Essential  Features  (Fig.  239a) 

Ilium  and  lumbar  sacral  segment 
Ischium  acetabulum  and  femoral  heads 
Pubis  and  symphysis 

Exposures 

1.  Ventro-dorsal 

2,  Dorso-ventral 

Difficulties 

1.  The  bones  are  at  an  angle  to  the  hori- 
zontal and  consequently  there  is  marked 
distortion 

2.  The  plane  of  the  pelvic  inlet  being  oblique 
to  the  plate,  makes  the  estimation  of  its 
diameter  difficult 

Ventro-Dorsal 
Posture  (Fig.  239b) 

Dorsal  decubitus 

Perfectly  horizontal 

Note :   marked  distortion  results  from  slight 
tilting. 

Immobilization 

Band  across  abdomen 

Tube  position 

Center  one-half  distance  between  umbilicus 
and  symphysis.  If  cone  is  used,  tilt 
downward  in  the  plane  of  pelvis 


Dorso-Ventral 


Posture 

Prone 


Immobilization 

L'nnecessary 

Tube  position 

Center  over  most  prominent  part  of  sacrum 

ILIUM 
Exposures 

1.  Ventro-dorsal    (preferable) 

2.  Dorso-ventral 

Immobilization 

Compression  cylinder 

Tube  position 

Nine   and   one-half    inch   cone,   outer   edge 
tangent  to  crest,  upper  edge  at  umbilicus 


Fig.  23ga 


Fic.  _'3yb. 


170 


RIBS-STERNUM 


RIBS 
(Ist  to   10th  inclusive) 

In  the  examination  of  the  ribs,  the  part  to 
be  radiographed  must  be  as  near  to  the  record- 
ing surface  as  possible. 

Essential  Features 

Head,   tubercle   and  neck   of    rib,   articular 
surface  for  transverse  process  of  the  vertebrae 
Vascular   groove 
Fibro-cartilages  (ossiiied) 

Exposures 
Posture 

Trunk,  horizontal  when  possible 

Anterior   ribs — dorsal-ventral 

Right     axillary  —  ventro-dorsal  —  second 

oblique 
Left   axillary — ventral-dorsal — first   oblique 
(Fig.  271) 

Immobilization 

By  cessation  of  respiration.  When  latter  im- 
possible, instantaneous  exposure 

Tube  Position 

Ventro-dorsal,  second  rib 
Dorso-ventral,  fourth  spine 
Oblique,    third    rib    and    sternum    or    post 
scapular  line 

Radiographic  hint :    Use  ray  of   low  pene- 
tration 


RIBS. 
(10th,   11th  and  12th) 


Exposures 
Ventro-dorsal 

Posture  (  See  kidney  examination) 
Dorsal  decubitus 
Thigh  flexed 
Shoulders  elevated 

Immobilization 

Compression  with  nine  inch  cone  with  loofah 
or  rubber  ball 

Tube  Position 

Lower  edge  of  nine  inch  cone  two  inches 
above  umbilicus 


STERNUM 

Essential  Features 

L  Sterno-clavicular  joint 

2.  Mandubricum 

3.  Gladiobus 

4.  Zyphoid 

Exposures 

Dorso-ventral  first  oblique,  right  sterno  clav. 
Dorso-ventral  second  oblique,  left  (best) 
Dorso-ventral  excentric 


Difficulties 

1.  The  bone  has  little  density 

2.  The  median  shadow  in  front  and  spine 
behind,  obscure  the  view. 

Dorso-Ventral    First    Oblique 
Posture 

Right     thorax     to     recording     surface     at 

obliquity  of  forty-five  degrees 
Vertical,  (sitting  or  standing)  or  horizontal 
with  sand  bags  under  right  shoulder 

Immobilization 

Cessation  of  breathing 

Tube  Position 

Central  ray  throtigh  posteriorscapular  line 

Dorso-Ventral  Second  Oblique 

Posture 

Left  thorax  to  recording  surface  at  obliquity 
of  forty-five  degrees.  Best  position.  Ver- 
tical (sitting  or  standing)  or  horizontal 
with  sand  bags  under  left  shoulder 

Immobilization 

Cessation  of  breathing 

Tube  Position 

Central  ray  through  posterior  scapular  line 

DoRSo- Ventral  Excentric 

Posture 

Prone,  plate  to  sternum 

Immobilization 

Cessation  of  breathing 

Tube  position 

Central  ray  through  right  posterior  scapular 
line,  opposite  second  dorsal  spine  directed 
fortv-five  degrees  downward  and  to  left 


HIP 


171 


LOWER  EXTREAIITV 

All  parts  to  be  radiographed  with  foot  in- 
verted. 

The  following  joints  are  to  be  studied: 
1.  Acetabular  femoral 
( 2.  Tibio-condylar 
]  3.  Tibia,  fibular,  upper 

4.  Tibia,  fibular,  lower 

5.  Tibia,  fibular,  astraguluni 

6.  Medio  tarsal 

7.  Tarsal  metat. 

8.  Metatarsal  phalangeal 


Hip 
Knee 


Ankle 


HIP  JOINT 
Essential  Features   (Fig.  240) 

1.  Neck,  head,  trochanters,  and  upper 
fourth  of  shaft 

2.  Ischial  tuberosity 

3.  Sacro-iliac  joint,  lower  part 

Exposures 

1.  Verttro-dorsal 

2.  Dorso-ventral  (brings  bones  nearer  plate 
— but  not  so  practical  a  view  as  ventro- 
dorsal) 

3.  Intero-external 

Ventro-Dorsal 
Posture 

With  iinrrsion  of  foot  (inner  rotation  of 
thigh) 

Neck  is  lengthened 

Greater  trochanter  prominent 

Lesser  trochanter  not  visible 

(Neck  lies  parallel  to  recording  surface) 

With  eversion  of  foot  (outward  rotation  of 
thigh) 

Head  of  femur  is  directed  inward  and  for- 
ward 

Neck   is   shortened 

Greater  trochanter  covers  neck 

Lesser  trochanter  prominent 

(Neck  does  not  lie  parallel  to  recording 
surface) 

Caution :  The  latter  appearance  is  found 
with  fracture  of  the  neck  in  which  eversion 
takes  place  and  fracture  line  may  be  obscured. 

Immobilization 

Foot  with  sand  bags,  compression  cone 

Tube  position   (Fig.  242) 

Five  inch  cone  with  upper  edge  just  under 
anterior  su]3erior  spine,  outer  edge  tan- 
gent to  outer  border  of  the  thigh.  Focus 
point  center  of  Poupart's  ligament 


Fig.  242 


172 


THIGH 


Fig.  243 


Fig.  244 


Note:  To  show  acetabulum  (hip  joint 
space)  the  upper  edge  of  cone  is  one  inch 
above  anterior  superior  spine  and  inner  edge 
in  median  hne.  Upper  surface  of  symphysis 
is  at  same  level  as  middle  of  acetabulum 

Dorso-Ventral 
Posture 

Prone,  upper  edge  of  plate  at  anterior  su- 
perior spine 

Immobilization 
Compression  cone 

Tube  position 

Five  inch  cone,  lower  edge  just  below  ischial 
tuberosity,  outer  edge  tangent  to  outer 
thigh 

To  obtain  hip  joint  space,  deviate  cone,  two 
inches  towards  median  line  at  level  of 
anterior  superior  spine  of  ilium 

Intero-External 
Posture 

On  side,  thigh  flexed,  to  right  angle  with 

body,  back  supported  by  sand  bags 
Plate   under   trochanter,    opposite   leg   sup- 
ported by  pillows 
Flexion  of  the  thigh  being  maintained  the 
body  may  be  tilted  back  after  the  lateral 
posture  is  assumed 

Immobilization 

Sand  bags  over  legs  and  thighs  and  foot 
Tube  position 

Central  ray  directed  obliquely  20  to  25 
degrees  through  greater  trochanter  from 
above  downward    ( Fig.   243 ) 

THIGH 

Essential  Features 

1.  Bone  detail 

2.  Differentiation  of  muscular  planes 

Exposures 

1.  Dorso-ventral 

2.  Ventro-dorsal 

3.  Lateral   (intero-external  easiest  arrange- 

ment) 

4.  Oblique — if   lateral   view    is    impossible, 

oblique  is  done  at  45  degrees 

Difficulties 

1.  Heavy  musculature 

2.  Distance  of  the  bone  from  the  plate 
Note :    It  is  frequently  necessary  to  make  a 

plate  of  a  localized  area  for  dift'erentiation  of 
the  lesion  which  has  been  isolated 


KNEE 


173 


1. 


KNEE 
Essential   Features    (Fig  245) 

Joint  spaces 

a)  Tibio  femoral 

b)  Tibio  fibular 
Peripatellar  bursal  spaces 
Popliteal   space 
Spines  of   tibia 


5.  Tibio — fibular  articulation 
Exposures 


Antero-posterior 
Intero-external 
(Easiest  arrangement, 
completely  overlap) 
Extero-internal 
Oblique 


Condyles  should 


5.  Postero-anterior 

Difficulties 

1.  Joint  space  is  oblique 

2.  Leg  and  thigh  must  be  horizontal  to  get 

joint  space 
Notes :  With  the  leg  extended,  the  joint 
space  is  at  the  level  of  the  lower  surface  of 
the  patella.  If  examining  for  bursitis  don't 
overexpose  or  overdevelop.  Calcification  of 
popliteal  arteries  may  be  seen  in  popliteal 
space.  Joint  bodies  may  be  visible  above 
patella  between  it  and  the  femur. 

Antero-Posterior 

Posture  (Fig.  246) 

Thigh  and  leg  must  be  horizontal 

Immobilization 

Fix  both  legs 

Tube  position 

Five  inch  cone,  upper  edge  of  cone  lJ/2  in- 
ches (4  cm.)  above  upper  edge  of  patella 

Interno-External 
Posture 

Trunk  on  same  hip,  plate  to  outer  side,  knee 
extended,  other  knee  extended,  abducted 
and  flexed 

Immobilization 

Sand  bag  over  leg  and  middle  thigh 

Tube  position 

Upper  edge  of  5"  cylinder  1^4"  above 
upper  edge  of  patella.  Patellar  shadow 
is  clear  of  condylar.  Central  ray  goes 
through  intercondyloid  spines 


Fig.  245 


Fig.  246 


174 


KNEE 


Fig.  247    (Schoenberg) 


Fig.  24S 


Externo-Internal 

Posture  (Fig.  247) 

Trunk  on  opposite  hip,  both  knees  flexed, 
plate  between  knees  supported  on  stool — 
knee  on  plate  horizontal 

Immobilization 

Both  legs 

Tube  position 

Same  as  above 

Oblique 

(Popliteal  Region,  Tibio-Fibular  Joint) 
Posture 

As  in  int.  ext.  view  (Fig.  248) 

Immobilization 

As  in  int. -ext.  view 
Tube  position 

5"  cylinder  directed  from  behind  forward 
into  popliteal  space 

Posterior-Anterior 
{ To  show  sagittal  view  of  patella  and  tibio- 
fibular joint) 
Posture 

Prone,  rotate  leg,  inward,  feet  over  edge 
of  table 

Immobilization 

Sand  bags 

Tube  position 

Axis  of  ray  directed  from  without  inward 

LEG 
Essential  Features 

1.  Tibia  and  fibula — entire  length 

2.  Inter-osseous  space  clear 

Exposures 
Posture 

1.  Antero-posterior — usual 

2.  Postero-anterior 

3.  Intero-external — usual 

4.  Extero-internal 

Immobilization 

Bandages  over  thigh 

Sand  bag  against  foot 

Note :  The  sagittal  views  must  be  made 
with  foot  inverted.  In  the  lateral  views  the 
axial  ray  must  be  directed  obliquely 

Intero-external — from  within  outward 

Extero-internal — from  without  inward 


LEG 


175 


ANKLE  JOINT 
Essential  Features  (Fig.  249) 

L  Joint  spaces 

2.  External  malleolus 
Interosseous  malleolus 
Internal  malleolus 

3.  Tendo  achillis 

4.  Os  calcis  and  astragulus 

Exposures 

1.  Antero-posterior 

2.  Intero-external 

3.  Oblique 

Difficulties 
Joint    space    at    distance    from    plate — ele- 
vate upper  part  of  plate  or  increase  target 
plate  distance 

Antero-Posterior 
Posture  (Fig.  250) 

Heel  to  plate — foot  inverted 

Immobilization 

Fix  at  knee  and  leg — sand  bag  against  foot 

Tube  position 

5"    cone    over    joint    space.      Incline    10° 

towards  foot 
Central  ray  through  line,  1"  above  external 

malleolus 

Intero-External  and  Extero-Internal 

Posture 

Internal  or  external  malleolus  to  plate — foot 
extended 

Immobilization 

Trunk  on  side — supported  by  sand  bags  to 

back 
Leg  and  foot  horizontal — sand  bag  over  calf 

Tube  position 

Lower  edge  of  cone  at  plantar  surface — 
back  edge  of  cone  tangent  to  posterior 
surface  of  heel 

Central  ray  through  internal  malleolus 

Oblique  (Fig.  252) 

(To   show   full  extent  of   external   malleolus 

and    interosseous    malleolus) 

Posture  (Fig.  251) 

External  malleolus  to  plate  slightly   above 

center 
Foot  extended — leg  parallel  to  plate 


TIOIALIS   POSTICUI 


Fig.  250 


176 


FOOT 


Fig.  251 


Fig.  252 


Fig.  252a. 


Immobilization 

As  usual 

Tube  position 

Incline  cone  5"  60' anteriorly  and  10°  down- 
ward. Central  ray  to  pass  through 
posterior  portion  of  astragulus,  from 
above  downward  and  from  behind  for- 
ward 


TARSUS 
Essential  Features  (Fig.  253) 

1.  Tarsal  bones 

2.  Intertarsal  joint  spaces 

Exposures 

1.  Supero-inferior 

2.  Extero-internal  i  lateral 

3.  Intero-external  )  oblique 

Difficulties 

Tarso-metatarsal    joint   not   easily   outlined 
Tarsals,    metatarsals    and    phalanges    have 
different  densities 

Supero-Inferior 
Posture 

Patient  sitting — for  medio-tarsal  bones  and 

tarso-metatarsal  joints 
Foot    flat,    plantar    surface    to    plate,   leg 

obliquely  backward 

Immobilization 

Bandages 

Tube  position 

Central  ray  through  base  of  third  metatarsal 

Ixtero-External.    Extero-Internal 
Posture  (For  flat  feet) 

Patient  sitting  or  standing 
Internal  or  external  surface  to  plate,  leg  ex- 
tended obliquely  backward 

Immobilization 

Pressure  of  leg 

Tube  Position 

Plate  vertically  to  one  side,  tube  to  opposite, 
through  navicularis 


TOES 


177 


Extero-Inteknal  or  Intero-External 

Posture 

Trunk  horizontal 

Foot  at  right  angles  to  leg 

Immobilization 

Bandages  and  cone  pressure 

Tube  position 

Central  ray  through  navicularis.  Extro- 
internal.  Central  ray  through  point  1" 
below  and  1"  in  front  of  external  mal- 
leolus. Intero-external — 1^"  below  and 
1"  in  front  of  internal  malleolus  5"  cone. 


METATARSUS  AND  PHALANGES 
Essential  Features 

1.  Metatarsol-phalangeal    and    interphalan- 
geal  joint  spaces 

Exposures 

1.  Supero-inferior 

2.  Infero-Superior      (Fig.   254a) 

3.  Oblique 

Supero-Inferior 
Posture 

Plantar  surface  to  plate  (Fig.  254) 

Immobilization 

Sitting  posture — leg   extended   backward 

Tube  position 

Central  ray  middle  of  3rd  metatarsal 

Oblique 
Posture 

Outer  side  of  foot  to  plate. 

Immobilization 
Bandages 

Tube  positioii 

Central  ray  directed  from  dorsum  to  plantar 
region  through  middle  of  3rd  metatarsal 


Fig.  253 


Fig.  254 


Fig.  254a. 


178 


CLAVICLE 


CLAVICLE 

Essential  Features  «, 

1.  Acromio-clavicular  joint 

2.  Sterno-clavicular  joint 

Exposures 

1.  Outer  third  examined  in  ventro-dorsal 

2.  Inner  third  in  dorso-ventral  ( see  shoulder) 
(inner  third) 

Dorso-Ventral 
Posture 

Vertical — chest  against  plate 

Immobilization 

Cessation  of  respiration 
Bandages 

Tube  position 

Central    rav   through   4th   dorsal    vertebrae 


Fig.  255 


Fig.  256.     (Albers-Schoenberg.) 


SCAPULA 
Posture 

Supine — plate    under    bone — arm    abducted 
to  level  of  shoulder — wrist  on  head 

Immobilization — Cessation    of    respiration 

Tube  position — Upper  edge  8"  cone,  1"  above 
point   of    shoulder — directed    inward 
Central  ray  through  3rd  intercostal  space  in 
anterior  axillary  line 


UPPER  EXTREMITY 

The  following  joints  are  to  be  studied : 

1.  Shoulder  iGleno-humeral 

( Acromo-clavicular 

Humero-ulnar 

2.  Elbow      Humero-radial 

Radio-ulnar 


3.  Wrist 


Carpo-radial 
Radio-ulnar 


4.  Carpo-metacarpal 

5.  Metacarpo-phalangeal 

Posture 

All  parts  to  be  elevated  to  level  of  shoulder 


SHOULDER 


179 


1. 
2. 
3. 


SHOULDER 

Essential  Features   (Fi| 

Acromo-clavicular   joint 
Gleno-humeral  joint 
Coracoid  process 

Difficulties 


255) 


1.  Incomplete  approximation  of  shoulder  to 
plate  because  of 

a)  Round  shoulders 

b)  Bandaging  or  cast 

2.  Avoiding  respiratory  movements 

a)  Induced  by  bandaging 

b)  Placing  hand  oUi  abdomen 

3.  Clavicle,  coracoid  and  acromion  lie  in 
different  planes,  hence  the  change  in  shadow 
at  slight  variation  of  tube  position. 

Posture 

1.  Arm  at  side  f  Vertical 

2.  Arm  abducted  to  90  degrees  f  Horizontal 

The  internal  condyle  of  the  lower  end  of 
humerus  indicate  the  direction  in  which 
the  articular  surface  of  the  head  points 

Exposures 

((a)   Gleno-humeral 

1.  Antero-posterior|(b^   Acromio-clavicular 

Joint  space  and  girdle  shown  in  best  rela- 
tion 

2.  Postero-anterior — shows  lesser  tuberosity 

better 

3.  Infero-superior.     This  view  permits  the 

viewing  of  the  coracoid  process 

Antero-Posterior 
a)  Humero-glenoid — Glenoid  cavity  is  directed 
outward  and  forward.    Humeral  head  is 
directed  slightly  backward 

Posture  ( Fig.  256,  II  Fig.  257) 

Shoulder  on  inclined  block  (45°).  If  peri- 
arthritis suspected,  rotated  outward. 

Point  of  shoulder  two  inches  from  upper 
and  two  inches  from  outer  side  of  plate 

Arm  to  side — forearm  midway  between  su- 
pination and  pronation.  Internal  condyle 
of  humerus  directed  inward 

Long  axis  of  bone  parallel  to  plate  and 
flat.     Head  inclined  to  opposite  side 

Sand  bag  under  opposite  shoulder  to  avoid 
slipping  of  body 

Immobilization 

Compression  with  cone  necessary  with  inter- 
position of  sponge 


Fig.  257 


Fig.  258 


Fig.  J59 


180 


SHOULDER 


Fig.   260. — Acromio-clavicular   view   of   shoulder 
showing  coracoid  process. 


EiG.  261 


Tube  position 

Central  ray  passes  four  inches  above  center 

of  joint — subacromial  depression      ^ 
Outer  edge  of  five  inch  cone. One  inch  above 
and  one  inch  to  outer  side  of  shoulder — 
incline  10°  from  without  inward 
Note :    The  inner  portion  of  the  anatomical 
neck  lies  at  the  junction  of  the  middle  and 
lower  third  of  the  glenoid  cavity.     In  marked 
abduction  the  anatomical  neck  lies   at  lower 
edge  of  the  glenoid, 
b.  Acromio-clavicular 

Essential  Features 

1.  Scapula 

2.  Acromio-clavicular  joint 

3.  Coracoid 

Posture  (Fig.  256,  II  Fig.  259) 
Trunk  and  shoulder  flat 
Arm  to  side,  forearm  midway  between  pro- 
nation  and   supination — Internal    epicon- 
dvle  directed  inward 
Immobilization 

Padding  to  cone,  which  is  in  contact  with 
chest 
Tube  position 

Central  ray  passes  four  inches  below  center 

of  joint. 
Five  inch  cone  tangent  to  outer,  and  upper 
curve  of  shoulder 

Postero-Anterior 
Posture  ( Fig.  261) 

Standing,    sitting   or   prone.     The   plate    is 

pressed   against   the   anterior   surface   of 

the   shoulder,    arm   to    side,   the    internal 

epicondyle  of  the  humerus  pointing  inward 

Immobilization 

Compression  with  cone  necessary  in  sitting 
and    standing    positions,    unnecessary    in 
prone  position ;  cessation  of  respiration 
Tube  position 

Five  inch  cone  tangent  to  upper  and  outer 
curves  of  shoulder 

IXFERO-SUPERIOR 

Posture 

Arm  rests  horizontally  on  support,  so  as  to 
bring  it  at  the  level  of  the  shoulder.     In- 
ternal epicondyle  of  the  humerus  pointing 
downward.     Plate  on  top  of  shoulder. 
Immobilization 

Cessation  of  respiration 
Tube  position 

Tube    under    axillary    space.     Central    ray 
directed  upward  and  inward 


ELBOW 


181 


HUMERUS  (SHAFT) 
Exposures 

1.  Antero-posterior 

2.  Externo-internal 

Extero-Internal 
Posture 

Sitting  at  side  of  table 

Elbow  fixed  as  near  right  angles  as  pos- 
sible, forearm  pronated,  arm  at  level  of 
shoulder 

Immobilization 

Forearm — bandages.    Sand  bag  on  shoulder 
Central  ray  through  middle  of  humerus 

Antero-Posterior 
Posture — Trunk  supine 

Arm  at  level  of  shoulder  with  olecranon  to 
plate 

Immobilization 

Sandbags  over  forearm 

Tube  Position 

Central  ray  to  outer  side  of  median  line 
of  arm 


ELBOW 

Essential  Features 

1.  Capitellum 

2.  Radial  head 

3.  Coronoid  process 

4.  Trochlea 

5.  Ementia  capitata 

6.  Condyles 

7.  Olecranon 

8.  Tuberosity  of  radius 

9.  Supratrochear  fossa 

Exposures 

1.  Extero-internal — radial  head  i)artly  cov- 
ered by  ulna 

2.  Antero-posterior — radial  head  visible 

3.  Extero-internal  oblique — to  isolate  radio- 
humeral  articulation 

Difficulties 

1.  Various  positions  not  always  possible,  be- 
cause of  deformity 

2.  In  children  do  lateral  view  first,  because 
painless 

3.  Dislocation  of  radial  head  may  be  over- 
looked in  lateral  view 

4.  Where  extension  not  possible,  place  point 
of  elbow  on  plate  and  focus  over  it 


182 


FOREARM 


Fig.  202 


Fig.  263 


Extero-Internal 
Posture  (  Fig.  262) 

Elbow  fixed  as  near  right  angle  as  possible 

Internal  condyle  to  plate 

Hand  prone.    Edge  of  table  to  side  of  chest 

Immobilization 

Sand  bag  to  forearm  and  shoulder 
Tube  Position 

Incline  central  ray  through  external  condyle 

Antero-Posterior 
Posture 

Body  supine,  arm  extended  and  flat 
Forearm    supination, — olecranon    in    center 
of  plate 

Immobilization 

Bandages 
Tube  Position 

Focal  point  2"   external  and   1"   belov,'  in- 
ternal condyle  of  humerus 

Oblique  (Fig.  263) 
Posture 

Elbow  flexed,  inner  condyle  to  plate,  fore- 
arm pronated 

Immobilization 

Bandages  over  forearm 
Tube  Position 

Central  ray  obliquely  from  without  inward 
through  olecranon 


FOREARM 
Essential  Features 

1.  Entire  lengths  of  bones 

2.  Interosseous  spaces 

Exposures 

1.  Antero-posterior 

2.  Postero-anterior 

3.  Lateral  R.  U.  or  U.  R. 

Posture 

Forearm  horizontal  and  at  level  of  shoulder 
Immobilization 

Bandages  at  wrist 
Tube  Position 

Central  ray  slightly  to  outer  side  of  midline 
of  forearm 


HANDS 


183 


WRIST  JOINT  AND  HAND 
Essential  Features 

1.  Intercarpal  joint  spaces 

2.  Radio-carpal  joint  spaces 

3.  Styloid  processes 

4.  Radio-ulnar  joint 

Exposures 

1.  Postero-anterior 

2.  Antero-posterior — shows  intercarpal  joint 


spaces  best- 
3.  Oblique  view 


-also  metacarpus  best 


Postero-Anterior 
Posture 

Palm  to  plate  (avoid  radial  deviation) 
For  carpal  scaphoid  and   semilunar   radial 

articulation,  hand  in  ulnar  deviation  and 

thumb  abducted  (Fig.  266) 

Immobilization 

Sand  bag  on  forearm — band  over  fingers 

Tube  Position 

Forward  edge  of  cone  over  middle  of  the 
proximal  phalanx  of  the  third  finger 

Central  ray  through  middle  of  interstyloid 
line 

Antero-Postertor  (Fig.  265) 

Posture 

Dorsum  of  hand  and  forearm  to  plate, 
thumb  abducted 

Immobilization 

Sand  bag  over  fingers 


Fig.  264. 


Tube  Position 

Central    ray    through    mid-line    at    level 
stvloid  of  radius 


Lateral 

a)  Extro-internal  (ulnar) 

b)  Intero-ext.ernal    (radial)    (Fig.  264) 


of 


Fig.  -265 

Figs.  264-265. — A  device  for  the  examination  of  the 
distal  end  of  the  radius.  "In  this  examination 
it  seems  desirable,  first,  to  make  the  examination 
if  possible  without  rotation  of  the  wrist;  and 
second,  that  the  plate  should  be  on  the  radial 
rather  than  the  ulnar  side.  Both  are  very  con- 
veniently provided  for  by  the  device  here  illus- 
trated, which  can  be  used  on  a  wide  chair-arm, 
as  shown  here,  or  by  placing  it  upon  a  table. 
A  slot  between  the  base  and  the  upright  serves 
to  hold  the  plate  in  the  vertical  position." 
(Bowen) 


184 


HANDS 


Fig.  266. 


Fig.   267. — Incorrect   arrangement.      The   joint   end.s 
of  the  bones  overlap. 


Fig 


20S. — Correct   arrangement.      The   joint    spaces 
are  clearly  visible. 


Extero-Internal 
Posture 

For  dislocation  of  semilunar,  ulna  to  i^cord- 
ing  surface.  Both  hands  with  palms  in 
contact  in  absolute  lateral  position 
For  lateral  view  of  trapezium  and  scaphoid, 
— ulna  to  recording  surface,  thumbs  in 
contact,  ulnar  sides  of  hand  slightly  separ- 
ated, palms,  therefore,  in  slight  prona- 
tion 
Immobilization 

Sand  bag  over  forearms 
Tube  Position 

Central  ray  over  st^doid  of  radius 
jMetacarpals 
Posture  (Fig.  268) 

Postero-anterior — palm  to  plate,  which  ex- 
tends  from  one-half   inch   above  tips   to 
two  inches  below  styloid  of  ulna 
Antero-posterior — dorsum  to  plate,   fingers 

separated 
Lateral — a)   radial,  b)   ulnar 
In  both   radial   and  ulnar  aspect  the   hand 
is  obliquely  placed — the  dorsal  aspect  in- 
clined towards  the  plate.     In  the  radial 
view,  oblique  elevation  of  hand  to  level 
of  shoulder  is  important 
Immobilization 

Bandage  to  plate 
Sand  bag  over  forearm 

Tube  Position 

Central   ray   throtigh   head   of   third   meta- 
carpal 

Phal.anges 
Exposures 

a)  Antero-posterior 

b)  Lateral 
Antero-posterior 

Posture — similar  to  above 

Tube  position — Similar  to  above.  If  correct 
the  metacarpo-phalangeal  and  interpha- 
langeal  joint  spaces  will  show 

Lateral 
Posture 

A  loofah  sponge  or  gauze  ball  is  placed 
in  the  palm  and  the  fingers  closed  about 
it.  This  will  show  all  the  proximal  and 
terminal  phalanges.  If  individual  views 
are  desired,  the  finger  is  extended  while 
the  others  are  flexed,  the  plate  being 
placed  between  it  and  the  finger  under- 
neath. For  the  phalanges  of  the  thumb, 
the  hand  must  be  elevated  and  the  thumb 
extended  into  a  lateral  posture 


CHEST 


185 


CHEST 
Essential  Features 

1.  The  plate  should  include  that  portion  of 
the  hody  extending  from  the  sixth  cervical  to 
the  lowermost  angle  of  the  costo-dia- 
phragniatic  sinus.  Laterally  the  very  periph- 
eral portions  of  the  ribs  and  their  soft  tissue 
covering  should  be  shown. 

2.  The  shadow  of  the  dorsal  vertebrae  must 
not  be  too  clearly  visible  through  the  heart 
shadow  nor  should  the  bone  detail  be  definable 
in  the  bones  of  the  shoulder  girdle.  The 
proper  contrast  and  details  will  then  exist  in 
the  plate 

3.  The  apical  portions  of  the  lungs  must 
not  be  obscured  by  rib  shadows  nor  the  heart 
by  diaphragm  shadows. 

4.  The  area  of  tracheal  illumination  must 
be  centrally  placed. 

5.  The  shadows  of  movable  structures,  dia- 
phragm, heart  must  be  sharp  and  clear. 

The  examination  of  the  chest  may  be  made 
in  the   following  postures : 


1.  Sagittal   dorso-ventral 

ventro-dorsal 

2.  Frontal  sinestro-dextral 

dextro-sinestral 

3.  Oblique   1st  dorso-ventral 

1st  ventro-dorsal 
2nd  dorso-ventral 
2nd  ventro-dorsal 


Centric 


Sagittal  Supero-Inferior 

Infero-Superior 

Sinestro-Dextral 

Dextro-Sinestral 


D.  V. 

or 
V.  D. 


Excentric 


Difficulties 

1.  Immobilization  is  often  impossible,  be- 
cause of  dyspnoea  and  restlessness,  particu- 
larly in  children.  This  must  be  overcome  by 
instantaneous  exposures. 

2.  Even  under  ideal  conditions  the  pulmonic 
and  cardiac  structures  are  in  constant  motion, 
hence  for  delineations  of  the  finer  details  of 
lung  structure  rapid  exposures  must  be  made. 


Fig.  269 


Fig.  270 


186 


CHEST 


3.  Approximation  of  part  to  plate  is  diffi- 
cult in  individuals  with  large  abdomens  or 
kyphotic  spines. 

4.  Because  of  the  convergence  of  the  shad- 
ows of  the  bony  structures  at  the  apical  por- 
tion of  the  chest  the  delineation  of  the  very 
apical  parts  of  the  lungs  is  not  possible  in  the 
general  examination. 

SAGITT-A.L 


Doeso-\'entr.\l 


Posture 


a)  Vertical 

This  necessitates  the  use  of  a  stative  or 
plateholding  frame.  The  simplest  form 
consists  of  an  iron  frame  inclosing  a 
wooden  block  eighteen  by  eighteen  inches. 
This  frame  moves  b}-  means  of  two  sleeves 
on  two  uprights  which  are  propped  against 
the  wall.  The  frame  should  be  counter- 
weighted,  for  convenience  in  up  and  down 
movements.  The  wooden  block  is  per- 
forated with  small  holes  set  an  inch  apart 
for  small  clamps  for  holding  plate  to 
board.  The  sensitized  plate  is  loaded  in 
both  black  and  red  envelopes  and  placed 
in  position  on  the  board,  being  maintained 
there  by  small  clamps  which  are  plugged 
into  the  holes  in  the  board. 

The  subject  is  placed,  with  the  anterior  chest 
against  the  plate  which  is  so  raised  as  to 
slightly  extend  the  neck  and  thus  insure 
a  view  of  the  apices.  The  chin  rests  on 
the  upper  edge  of  the  frame.  The  arms 
are  placed  on  the  frame  supports  which 
are  clamped  to  the  wall  in  such  a  way  as 
to  elevate  them  slightly  above  the  level  of 
the  shoulder.  In  obese  patients  it  may 
become  necessary  to  incline  the  plate  to- 
wards the  chest  in  order  to  obtain  closer 
approximation.  The  arms  are  placed  for- 
ward on  the  frame  supports  which  are 
clamped  to  the  wall,  the  scapula  thus 
being  drawn  away  from  the  posterior 
chest   (Fig.  269).  ' 

b)  Horizontal 

The  objection  to  examination  in  this  posture 
is  the  high  position  in  which  the  dia- 
phragmatic domes  are  showm,  w^hich  cover 
the  lower  part  of  the  heart  shadow.  The 
chin  hangs  over  the  edge  of  the  table. 
The  plate,  backed  by  a  piece  of  board,  is 
placed  at  the  very  edge  of  the  table.  The 
chest  is  placed  thereon  with  the  chin  on 
its  upper  edge,  the  arm  hanging  to  the 
side  of  the  table. 


Immobilization 

Active  immobilization  of  the  diaphragm  and 
chest  wall  is  accomplished  by  a  cessation 
of  respiration  in  a  normal  pause  between 
inspiration  and  expiration.  Passive  im- 
mobilization may  be  practised  by  the  use 
of  canvas  bands.  In  the  horizontal  pos- 
ture fixation  is  rarely  necessary  except  in 
children.  The  weight  of  the  body  is  suf- 
ficient to  hold  the  chest  firmly  against 
the  plate.  In  infants  both  hands  are 
brought  over  the  head  and  held  against 
the  side  of  the  head  by  one  hand,  while 
the  pelvis  is  immobilized.  \\'here  this  is 
difficult  or  impossible  an  instantaneous 
exposure  must  be  made. 

^^'here  extreme  speed  is  necessary  in  sub- 
jects who  cannot  or  will  not  cease  respira- 
tory movements  or  when  an  unusually 
long  tube  plate  distance  is  used,  as  in 
teleoroentgenographic  work,  the  sensitized 
plate  is  placed  with  its  sensitive  surface 
against  an  intensifying  screen  and  both 
suitably  enclosed  either  in  a  special  cas- 
sette or  in  the  regulation  red  and  black 
envelopes.  The  plates  are  so  placed  that 
the  ray  tranverses  through  the  glass  side 
of  the  plate  to  the  emulsion. 

Tube  Position 

The  recording  surface  and  subject  remain- 
ing in  the  same  position,  considerable 
variation  in  the  appearance  of  the  sagittal 
picture  of  the  chest  is  produced  by  a 
change  in  the  position  of  the  tube. 

The  central  ray  is  directed  in  all  the  pos- 
tures through  the  level  of  the  spine  of 
the  fourth  dorsal  vertebrae.  The  rela- 
tionships between  the  thoracic  structures 
thus  obtained  is  approximately  normal. 
In  the  ventro-dorsal  this  corresponds  to 
the  second  intercostal  space. 

Vextro-Dorsal 

Posture  (Fig.  270) 

The  most  favorable  posture  for  this  view 
is  the  horizontal  one.  The  arms  are 
clasped  on  the  head,  the  elbows  being 
drawn  well  forward,  a  small  part  of  the 
plate  should  be  seen  above  the  supraclavi- 
cular fossae 

Immobilization 

As  above 

Tube     position — Central     ray    through    3rd 
chondro-sternal  junction 


CHEST 


187 


Frontal  \'ie\vs 

Sinestro-dextral    and    dextro-sinestral,    the 
latter  preferable. 

Posture   (Fig.  273) 

Vertical.  The  arms  of  the  patient  elevated 
and  extended.  The  plate  is  placed  to  the 
side 

Tube  Position 

The  central  ray  is  directed  into  axillary 
space 

Oblique  \'ie\vs 
First  Oblique  V'entro-Dorsal 
The  oblique  view  (Fig.  271),  is  import- 
ant for  the  examination  of  the  esophagus  and 
the  thoracic  portion  of  the  spine.  This  view  is 
less  favorable  for  the  heart  and  vessels,  since 
the  heart  and  vessel  shadows  are  enlarged 
and  indistinct.  The  horizontal  posture  is  the 
more  favorable  for  the  examination. 

Posture 

The  body  rests  on  the  left  side,  the  left  arm 
being  outstretched,  the  right  arm  above 
being  placed  over  the  head  to  grip  the 
table  top.  The  upper  thigh  and  leg  are 
thrown  forward  over  the  under.  A  sand 
bag  is  placed  behind  the  gluteal  region 

Tube  position 

The  central  ray  is  directed  through  right 
mammar\-  line  at  the  level  of  the  second 
cartilage 

First  Oblique  Dorsal-Ventral 
Posture 

The  vertical  posture  is  most  favorable  for 
this  view.  The  patient  stands  with  his 
right  shoulder  and  right  chest  to  the  sta- 
tive,  the  right  arm  being  around  the 
stative,  the  left  being  placed  above  the 
head 
Tube  Position 

The  tube  is  centered  at  the  level  of  the 
fourth  dorsal  vertebra  in  the  mid-scapular 
line 

Second  Oblique  Dorsal  Ventral 
The    second   oblique   direction    (Fig.    272), 
principally  useful  for  the  examination  of  the 
heart,  aorta  and  mediastinum  and  the  upper 
portion  of  the  esophagus. 

Posture 

The  most  convenient  posture  is  the  vertical 
posture.  The  left  chest  is  placed  against 
the  plate  in  the  left  arm  encircling  the 
stative.  The  right  arm  is  placed  on  the  head 


Fig.  271.- 


-Body  in  position   for   ist  oblique  ventro- 
dorsal view  of  chest. 


1=1        I 


Fig.  272 


188 


ESOPHAGUS 


Fig.  273 


Fig.  274 


Tube  Position 

Behind  right  shoulder.  The  exposure  is 
made  during  deep  inspiration  «» 

Second  Oblique  Ventro-Dorsal 
Posture 

The  most  convenient  posture  is  the  horizon- 
tal. The  body  rests  on  the  right  side  with 
the  left  shoulder  elevated.  The  left  arm 
over  the  head.  The  left  knee  over  the 
right 
Tube  position 

Central  ray  through  left  mammary  line  at 
the  level  of  the  second  cartilage 

EXCEXTRIC 

Sagittal  view  with  left  or  right  excentric 
tube  position.  As  in  the  sagittal  views 
the  plate  is  placed  directly  against  the 
body,  but  the  tube  is  so  placed  that  the 
rays  strike  the  chest  at  an  angle  of  from 
30  to  45°.  The  examination  may  be  made 
in  the  ventro-dorsal  or  dorso-ventral 
position 

ESOPHAGUS 
Essential   Features 

1.  The  retrocardiac  oortion  of  the  pulmonic 
field 

2.  The  lower  third  of  the  cervical  region 

3.  The  oblique  view  of  heart  and  entire 
aorta 

4.  The    left    diaphragm 

5.  Outline  of  walls  in  peristaltic  activity 
and  in  relaxation  from  epiglottis  to  cardia. 

Postures 

Vertical       [ 

Horizontal  j 

General  view —  1st  oblique  ventro-dorsal 

For  upper  esophagus — 1st  oblique  dorso- 
ventral 

For  lower  esophagus — 1st  oblique  ventro- 
dorsal 

For  lower  esophagus — 2nd  oblique  dorso- 
ventral 

Difficulties 

1.  Peristalsis  is  initiated  by  swallowing  and 
the  rapidity  of  movement  demands  short  ex- 
posure with  intensifying  screen. 

2.  The  gullet  can  be  outlined  only  after 
ingestion  of  contrast  mixture  which  coats  the 
esophageal  wall  with  a  coating  of  contrast 
salt.  Bismuth  subcarbonate  Y2  ounce  in 
mucilage  acacia  one  dram 

Cervical  Portion  of  Esophagus 
Posture 

Prone,  head  to  side,  chin  elevated 


ESOPHAGUS 


189 


Immobilization 
Head  clamps 
Tube  Position 

Central  ray  opposite  cricoid 

Ti-ioKACic  Portion 

1.  Ventro-dorsal — 1st  oljlique 
Posture   (Fig.  218) 

Trunk  in  horizontal  position  on  left  side,  at 
forty-five  degrees,  right  shoulder  ele- 
vated, left  arm  extended,  right  arm  over 
head,  grasping  table,  right  leg  thrown 
over  left.  Sand  bags  behind  lumbar 
region,  head  on  sand  bag 
Immobilization 

x^fter    swallowing    eiTort,    cessation    of    all 
motion  and  respiration  after  deep  inspira- 
tion 
Tube  Position 

Central  ray  through  level  of  second  carti- 
lage, and  nipple  line 

2.  Dorso-ventral — 1st  oblique 
Posture 

Trunk  prone  on  right  side  at  forty-five  de- 
grees, left  shoulder  elevated,  head  resting 
on  right  parietal  and  mastoid,  right  arm 
around  head,  left  arm  over  head,  grasp- 
ing table  edge,  right  leg  flexed  and  left 
leg  behind  and  extended 
Immobilization 

As  above 
Tube  Position 

Central   ray   through    mid-scapular    line    at 
level  of  fourth  dorsal 

ABDOMEN 

Gastro-Intestinal  Tract 

Essential  Features    (Fig.  276) 

1.  The  domes  of  both  diaphragms 

2.  The  lower  border  of  the  liver 

3.  The  pelvic  inlet 

4.  The  gastro-intestinal  tract  outlined  by 
contrast  media  administered  after  preparation 
Posture 

Vertical        I  ,  , 

Horizontal*  ^Jo''^o-^^"^'"^''l 


Oblique 


(D.  V.  2nd 
■|D.  V.  1st 

For   caecum   and   appendix   lower   sigmoid 
and  rectum  ventro-dorsal  views  are  valuable 

Difficulties 
Constant  movement  of  stomach  and  intes- 
tines demands  short  exposures  for  delinition. 
This    necessitates    the    use    of     intensifying 
screens. 


Fig.  275 


Fig.  J70 


190 


GASTRO-INTESTINAL  TRACT 


TECHNIQUE    FOR    RADIOGRAPHIC   EXAMINATION  OF  THE 
GASTRO-INTESTINAL  TRACT 


1.  Residue  Examination 


meal     and 


b.  Meal 


a.  Preparation — no     evening 
enema 

Carboh_vdrate  400  gms. 
Bis.  subcarb.  60  gms. 

c.  Examination — Six   hours    after   inges- 
tion 

d.  Posture — Vertical 

e.  Exposure — Dorso-ventral 

2.  Sedimentation  Test 

a.  i\Ieal — barium  sulphate  1  oz.  in  water 
4  oz. 

b.  Examination  during  ingestion 

c.  Posture — Vertical,   right   lateral,   hori- 
zontal 

d.  Exposure  Dorso-ventral  "  after  palpa- 
tion " 

3.  Morphology  ExAiiiNATioN 

a.  Meal — barium  sulphate  3  oz.  in  butter- 
milk 

b.  Examination  directly  after   ingestion 

c.  Posture — Vertical  —  horizontal  —  R. 
Lateral 

d.  Exposure — Dorso-ventral 


4.  Motility  Examination — Intestinal 

a.  Preparation — Regular    diet,    no    purge 
or  enema 

b.  Examination — Six    hours    after    meal, 
also  at  10,  12,  18,  24,  36  and  48  hours 

c.  Posture — Vertical  and  horizontal 

d.  Exposure — Dorso-ventral 

Ventro-dorsal  for  caecum, 
sigmoid  and  rectum 

Left  lateral — for  study  of 
caecal  mobility 


Purpose 

To  study 

1.  a.   Stomach  Motility  and  Secretion 
b.  Intestinal  iMotility 


a.  .Stomach 

1.  Tone 

2.  Niche 

3  Antral  activity 
4.  Pyloric  patency 


3.  a. 

Stomach 

1.  Type    . 

2.   Size 

3.  Axis 

4.  Position 

5.  Outline 

6.  Mobility 

7.  Peristalsis, 

b. 

Duodenum 

1.  Type 

2.  Ske 

3.  Outline 

4.  Mobility 

5.  Peristalsis 

4.  a. 

Small  intestine 

1.  Motility 

b. 

Large  intestine 

1.  Size 

2.   Shape 

3.  Position 

4.  Peristalsis 

GALL  BLADDER 


191 


Dorso-Ventral — Vertical 
Posture 

Abdomen  against  plate,  the  ujiper  part  be- 
ing at  level  of  nipple.  Plate  against  the 
stative,  arms  grasping  side  of  plate  holder 

Immobilization 

Cessation  of  respiration.    Binder  across  loins 

Tube  Position 

Center  of  spine  at  level  of  posterior  inter- 
cristal    line 


Posture 

Vertical 
Horizontal 
Left  lateral 

Exposures 
For  abdominal  and  iliac  colons,  dorso-ven- 


tral 


For  pelvic  colon — ventro-dorsal 

For  mobility  test — dorso-ventral  lateral 
(right  and  left)  and  Irendelenberg  posi- 
tions 


Dorso-A'entral — Horizontal 
Posture 

Body  prone.  Plate  to  abdomen.  Arms 
hanging  over  table  edge.  Lower  end  of 
14  X  17  plate  below  symphysis. 

Immobilization 

As  above 

Tube  Position 

As  above 


Dorso-Ventral — Lateral 
Posture 

Body   on    right    side    horizontal.      Plate   to 
abdomen 

Immobilization 

Plate  against  support.     Head  on  right  arm, 
left  arm  grasping  support 

Tube  Position 

As  above 

COLON 

Examination  by  Enema 

Preparation 

The  colon  should  be  washed  out  by  a  cleans- 
ing enema,  and  the  following  contrast  mixture 
should  be  administered : 

Barium  sulphate,  4  ounces 
Mucilage  acacia,  2  ounces 
Warm  water,  3  pints 

This  is  placed  in  a  metal  container  and  con- 
stantly stirred.  The  small  rubber  tip  is  in- 
serted in  the  rectum  and  the  contents  allowed 
to  flow  in  from  a  height  no  greater  than  two 
and  one-half  feet  above  the  patient.  By  gentle 
massage  the  enema  is  pressed  into  the  caecum. 
The  colon  is  studied  fluoroscopically  during 
the  flow  of  the  enema  for  spasms,  tumors, 
Icinks  due  to  bands  and  adhesions. 


GALL  BLADDER 
Essential   Features 

10th,  Uth  and  12th  ribs 

Right  half  of  1st  and  2nd  and  3rd  lumbar 
vertebrae 

Lower  border  of  liver 

Right  kidney 

Gall  bladder — it  is  contended  that  the  gall 
bladder  is  visible  only  under  pathological 
conditions  but  this  has  not  been  proven 

Positions 

Post.  ant. — horizontal  and  vertical 
Oblique — horizontal 


Fig.  277. — Radiograph   showing   the   region  occupied 
by  the  gall  bladder  in  the  horizontal  posture. 

Difficulties 

But  fifty  per  cent  of  calculi  can  be  shown 
Calculi  do  not  have  sufficient  liiue  content 
and  may  show  in  some  plates  and  not  on 


URINARY  TRACT 


-Fig.  jyS 


Fig.  279 


others,    hence   multiple   exposures    neces- 
sary 
Where  calculi  do  not  show  indirect  evidence 

(cholecystitic  inflammation)   may  be  obtained 

by  gastro-intestinal  examination 

Postero-Anterior    (Horizontal) 
Posture 

Prone,  chest  slightly  elevated,  plate  under 
right  hyperchondriac  region 

Immobilization 

Binders  over  buttocks.  Cessation  of  respir- 
ation 

Tube  Position 

Central  ray  passing  just  below  right  costal 
border — Four  inch  cone — 4"  from  skin 

Posterior-Anterior    Oblique 

Posture 

Trimk  bent  and  slightly  rotated  to  left  to 
widen  region  between  lower  right  ribs  and 
iliac  crest.     Lower  part  of  plate  elevated 

Tube  Position 

Central  ray  76-60  degrees  to  plate,  and 
directed  outward.  Cylinder  resting  pos- 
teriorlv  on  right  costal  border 


URINARY   TRACT 
Essential   Features 

10th,   11th  and   12th  ribs 
Psoas  muscles 
Transverse  processes 
Kidney  outlines 

Difficulties 

Intestinal   contents   obscure   structural  out- 
lines, hence  preparation  necessary.    Vege- 


table    cathartic     the     night     befor 


and 


enemas  the  next  morning  until  bowels 
empty.     No  food  before  examination 

Urate  of  soda  calculi,  cast  no  appreciable 
shadow 

Extraiu"eteral  or  renal  shadows  simulate 
those  of  calculi,  hence  catheterization  and 
injection  of  contrast  media  sometimes 
necessary.     Collargol   10% — Thorium 

Immobilization  of  kidneys  must  be  accomp- 
lished by  pressure  on  abdomen,  which 
also,  displaces  gut.  Kidneys  move  yi 
inch  in  respiration 

Exposures 
Upper  lU'inary  tract — dorso-ventral  "|  Supine 
Lower  urinary  tract — dorso-ventral    >     or 


URINARY  TRACT 


193 


Fig.  281. — The  centering  point  for  each  kidney  is  a 
point  half  way  between  the  ziphoid  and  the 
umbiHcus  and  2  inches   from  middle  line. 


b) 


of      respiratory 


KIDNEYS  AND  UPPER  URETERS 
Posture 
Ventro-dorsal — supine — shoulders    elevated, 
knees  flexed.     If  the   individual  kidneys 
are  to  be  examined,  8  x  10  plate  is  placed 
under  the  lumbar  region  so  that  Yz  the 
plate  is  below  last  rib.     The  upper  ureter 
is  then  examined  by  a  second  8x10  plate 
so  placed  that  its  upper  edge  is  two  inches 
above  highest  point  of  iliac  crest  and  its 
inner  edge  in  mid-line.     ( P""igs.  282,  283). 
If  10x12  plate  is  used  it  is  placed  broad- 
wise the  lower  border  of  the  plate  being 
at  a  plane  through  the  umljilicus 
Immobilization 

Compression  of  upper  abdomen 
a) 

1)  Inflated  rubber  ball  (preferred) 

2)  Loofah  sponge 

3)  Aluminum  bowl 

4)  Canvas  band 
Voluntary — cessation 

movements 
Tube  Position 

For  single  kidneys,  five  inch  cone  under 
anterior  ribs  inclined  30  degrees  cephal- 
ward 
For  both  kidneys  and  upper  ureters  eight 
inch  cone  with  ball  under  lower  ribs,  in- 
clined ten  degrees   (Fig.  279) 

LOWER  URETERS  AND  BLADDER 
Posture 

Ventro-dorsal — knees  elevated.  Plate  ( 10 
X  12)  with  lower  edge  one  inch  below 
gluteal  fold.  If  individual  ureters  are 
examined  the  lower  edge  of  the  plate 
(8x10)  is  just  below  gluteal  fold.  (Fig. 
278) 

Immobilization 

As  aljove 
Tube  Position 

Eight  inch  cone,  lower  edge  over  symphysis 
Incline  ten  degrees  downward 
For    single    ureter — five    inch    cone.      ( Fig. 
284)      For   both    tu'eters — upper   edge    5 
inch  cone  Ij.-!  inch  above  umbilicus 

BLADDER   (Dorso- Ventral) 
Posture 

Dorso-ventral — body  prone,  incline  block  23 
degrees   under   lower   alidomen   so   as   to 
raise  pelvis  (Fig.  284) 
Immobilization 

Cessation  of  respiration 
Tube  Position 

Five  inch  cone :  lower  edge,  at  tip  of  coccvx 


194 


BLADDER 


V 


Fig.  283 

The  prone  position  for  kidney  examination 
is  utilized  in  the  fluoroscopic  examination 
of  the  urinary  tract 


Fig.  284 

Tube  Position 

Underneath  table 

Focal  point  just  above  umbilicus 


KIDNEYS  AND  UPPER  URETERS 

Posture 

Prone — on  canvas  topped  table,  on  inflated 
spherical  rubber  ball  6"  in  diameter 
placed  between  lower  ribs  and  crests  of 
iliac.  Arms  over  edge  of  table.  Plate  on 
back — held  in  position  by  sandbag 

Immobilization 

Pressure  of  body  on  ball.  Cessation  of  res- 
piration 


LOWER  URETERS  AND  BLADDER 

Posture 

As  above 


Immobilization 

As  above 

Tube  Position 

Central  rav  2Vj' 


above  symphysis 


CHAPTER  XVni 
THE  EXPOSURE 

The  problem  in  the  production  of  the  radio- 
graph is  to  obtain  fine  definition,  a  maximum 
of  detail,  minimal  distortion  and  proper  con- 
trast. To  obtain  the  above  characteristics 
there  is  necessary : 

1.  Rays  of  proper  quality   (penetration). 

2.  Rays   of    sufficient   quantity    (intensity). 

3.  Proper  tube  plate  distance. 

4.  A  focal  spot  of  minimum  size. 

5.  Exposure  of  proper  duration. 

1.     Ray  Quality 

The  x-rays  penetrate  substances  in  inverse 
proportion  to  their  density.  By  density  of  tis- 
sue is  really  meant  the  absorption  power  which 
a  tissue  has  for  the  x-rays.  The  more  opaque 
the  substance  is  to  the  x-ray  the  greater  the 
absorption  of  the  x-ray  by  this  particular  tis- 
sue, the  less  the  quantity  which  is  permitted 
to  pass  through,  the  less  the  effect  on  the 
recording  surface  of  the  sensitized  emulsion 
of  the  plate  or  fluorescent  screen. 

On  the  other  hand  the  more  transparent  the 
substance  the  less  the  absorptive  power  for 
the  x-ray,  the  greater  the  quantity  of  the  emer- 
gent ray,  the  more  actively  the  recording  sur- 
face is  affected. 

In  a  general  way  it  may  be  stated  that  the 
higher  the  vacuum  of  the  tube  the  more  pene- 
trating the  emergent  rays.  The  tube  which 
generates  rays  of  only  low  penetrative  power 
is  called  a  soft  tube  and  emits  soft  rays,  while 
that  which  emits  rays  of  great  penetrating 
power  is  called  a  hard  tube  and  emits  hard 
rays.  "  Hard  "  and  "  soft  "  are  photographic 
terms  which  have  been  utilized  in  x-ray 
nomenclature.  The  quality  plays  an  import- 
ant part  in  the  determination  of  contrast. 
Plates  made  with  a  very  soft  tube  have  coir- 
trast  without  detail.  Plates  made  with  a  very 
hard  tube  have  detail  without  contrast.  The 
maximum  quantity  of  both  exists  in  the  best 
radiosraph.      The     tube,     which     is     neither 


too  hard  nor  too  soft  is  called  a  medium  tube. 
'It  is  this  tube  which  has  its  greatest  field  of 
applicability  in  the  study  of  the  structures  of 
the  human  body. 

The  aim  is  to  establish  on  the  recording  sur- 
face a  record  of  tissue  densities  in  their 
relative  values. 

Therefore,  for  the  delineation  of  the  various 
parts  rays  of  varying  penetration  are  needed. 
The  penetration  of  the  rays  necessar}'  to 
delineate  the  structures  of  the  chest  would  be 
less  than  those  necessary  for  the  head,  because 
of  the  lesser  density  of  the  chest.  The  rays 
required  for  the  study  of  the  structures  of  the 
body  should  not  have  less  penetration  than 
that  which  is  produced  by  a  tube  whose 
vacuum  equivalent  is  a  three  inch  gap  nor 
more  penetration  than  is  produced  by  a  seven 
inch  tube.  This  corresponds  to  a  voltage  de- 
mand of  40,000  to  80,000.  The  aim  should  be 
to  obtain  the  particular  penetration  neces- 
sary to  outline  the  structures  with  the  mini- 
mum voltage. 

In  the  study  of  photographic  density  it  has 
been  stated  that  this  depends  on 

Mill.  Xvoltage-  X  time 
distance- 

If  these  are  given  numerical  values,  the 
amount  of  radiation  is  given  an  arbitrary 
value  in  units.  This  permits  comparison  as 
far  as  photographic  effect   is  concerned. 

The  photographic  elfect  varies  as  the  square 
of  the  voltage. 

If  the  other  factors  are  kept  constant,  the 
ratio  of  exposure  time  to  voltage  necessary  to 
produce  a  similar  density,  may  be  expressed  as 
follows : 


Gap 

Time 

2  inches 

(30  k.  V.) 

1.3  sec. 

0 

(40  k.  V.) 

1.0     " 

4       " 

(50  k.  V.) 

.6     " 

5       " 

(60  k.  V.) 

.4     " 

6       " 

(70  k.  V.) 

.3     " 

No  increase  in  time  can  compensate  for  a 
lack  of  penetration  in  the  production  of  the 


[195] 


196 


THE  TUBE  PLATE  DISTANCE 


radiograph,  though  it  does  affect  the  photo- 
graphic density  of  the  shadow  of  the  part 
actually  penetrated. 

2.  Ray  Quantity 

The  milliamperage  sought  is  that  which 
at  a  proper  voltage  will  make  a  good 
radiograph  within  an  allowable  time  limit. 
With  a  certain  penetration  the  time  will 
depend  on  the  milliamperage.  Thus  with 
a  tube  of  a  definite  penetration,  thirty  milli- 
amperes  and  an  exposure  of  four  seconds, 
120  milliampere  seconds,  may  give  the  re- 
quired density  and  contrast.  The  same 
density  and  contrast  will  be  produced 
with  the  same  tube  energized  by  the  same 
voltage  by  sixty  milliamperes  in  two  seconds 
or  by  one  hundred  and  twenty  milliamperes 
in  one  second.  The  energy  falling  on  a 
given  area  per  unit  of  time,  other  factors 
being  constant,  increases  in  direct  proportion 
to  the  current.  But,  though  the  density  and 
penetration  are  the  same  on  the  plate  made 
with  thirty  milliamperes  and  four  seconds,  the 
required  definition  and  detail  is  absent,  be- 
cause the  time  (four  seconds)  may  be  too 
long.  The  one  second;  120  milliampere  plate, 
however,  gives  the  required  negative.  The 
less  penetrative  the  rays,  the  larger  the  milli- 
ampere-second  factor  necessary  for  the  pro- 
duction of  the  same  density. 

3.  Tube  Plate  Distance 

The  importance  of  this  as  a  factor  in  correct 
radiography  is  two-fold.  Firstly,  the  proper 
target-plate  distance  is  necessary  to  avoid  dis- 
tortion. Secondl}',  the  intensity  of  the  x-rays 
diminishes  inversely  as  the  square  of  the  dis- 
tance. A  twenty  inch  target-skin  distance 
results  in  a  certain  variation  of  the  target-plate 
distance  for  various  parts  but  makes  for 
minimal  distortion.  Thus  the  plate  under  the 
hand  would  be  at  twenty-one  inches  from  the 
target,  under  the  knee  24,  under  the  chest 
28,  etc. 

Occasionally  the  magnification  of  the 
shadow  of  a  structure  in  the  usual  examina- 
tion is  not  without  its  value.    \Mien  a  cvlinder 


or  cone  is  used,  an  increased  distance  is  also 
necessary,  if  the  entire  part  is  to  be  included 
in  the  particular  plate  utilized.  «» 

The  distance  affects  the  time  factor  as 
follows :  if  at 

20  inches   the   time   factor   is  1 

15  .56 

16  .6+ 

17  .72 

18  .81 

19  .90 

21  1.10 

22  1.21 

23  1,32 

24  1.44 

25  1 . 56 

T.\BLE    XIV 

To  estimate  the  exposure  for  teleroentgeno- 
graphic  work,  if  current  and  voltage  is 
unchanged  the  same  intensity  will  be  ob- 
tained if  the  time  is  increased  as  the  square 
of  the  distance.  Thus  if  at  the  distance  of 
24  inches  jA  second  is  necessary  to  get  a  well 
exposed  chest  plate  at  72  inches  or  3  times 
the  distance  the  radiation  received  will  be  but 
l/9th  and  therefore  9  x  jA  or  4^4  seconds 
would  be  necessary.  If,  however,  an  inten- 
sifying screen  is  used  which  permits  the 
shortening  of  exposure  six  times,  the  exposure 
may  be  1/6  of  4J'2  seconds  or  ^4  seconds. 

4.  Focal  Spot 

The  smaller  the  focal  point  or  point  of 
emission  of  the  x-rays  on  the  target,  the  finer 
the  definition,  other  factors  being  the  same. 
Besides  this,  the  limitations  to  energy  input 
imposed  by  the  target  demand  consideration. 
The  fine  focus  Coolidge  tube  is  three  mm.  in 
diameter  and  will  utilize  from  twenty  to  thirty 
milliamperes,  at  a  certain  voltage.  A  short 
exposure  period  is  thus  not  possible  if  the 
correct  values  are  to  be  obtained.  A  broad 
focus  Coolidge  tube  being  ten  mm,  in  diameter 
will  utilize  three  and  one-third  times  the  energy 
-—65  to  100  milliamps. — under  the  same  con- 
ditions and  permit  the  shortening  of  the  ex- 
posiu-e  time,  but,  if  used  at  the  same  target 
j)late    distance   will   give   poor    definition. 


TIMING  OF  EXPOSURE 


197 


Therefore,  the  technique,  which  utiHzes  a 
sharp  focus  (efficiently  diaphragmed)  Cool- 
idge  tube  at  the  usual  target-skin  surface 
distance,  is  a  long  exposure  technique  and  its 
field  of  usefulness  is  limited,  therefore,  to  the 
examination  of  structures  where  no  movement 
takes  place.  A  short  exposure  technique  is 
only  possible  with  a  medium  or  broad  focus 
Coolidge  tube.  In  the  radiography  of  moving 
structures,  thorax,  gastro-intestinal  tract  or 
in  children,  where  immobilization  is  difficult 
and  ra]_)idity  of  exposures  become  necessary, 
the  "fine  focus"  tube  (3  mm.),  capable  of 
utiHzing  20  milliamperes  is  no  longer  applic- 
able, for  a  larger  energy  input  becomes  neces- 
sary. With  a  milhamperage  of  65  to  110 
milliamperes  and  with  voltages  ec|uivalent  of 
spark  gaps  varying  from  5  to  6  inches,  rapid 
exposures  of  chest  and  gastro-intestinal  tract 
may  be  made,  ^^'hile  radiographs  of  the 
gastro-intestinal  tract  fulfil  requirements,  the 
chest  plates  made  under  these  conditions  of 
focal  point  and  distance  do  not  attain  the 
standard  required  by  the  latest  and  best  radio- 
graphic practise. 

The  focal  spot  on  a  fine  focus  gas  tube  is 
\y2  mm.  in  diameter.  With  the  gas  tube,  how- 
ever, though  finer  focusing  is  possible  the 
limitations  to  the  quality  of  energy  input  do 
not  exist  to  the  same  degree,  so  that  when 
speed,  detail  and  sharpness  of  image  are  re- 
quired the  gas  tube  is  preferable. 

5.   Timing  of  Exposure 

An  accurate  record  of  tissue  density  in  tone 
value  and  a  sharply  defined  true  shadow  of 
tissue  form  would  be  relatively  simple  with  a 
parallel  ray,  but  radiography  has  to  do  with 
a  divergent  ray.  The  homogeneity  of  a 
bundle  of  divergent  rays,  falling  upon  a  given 
surface  may  be  increased,  first,  bv  decreasing 
the  focal  spot,  secondly,  by  increasing  the  tar- 
get recording  surface  distance.  The  result  of 
the  application  of  one  or  both  of  these  con- 
ditions is  to  increase  the  sharpness  of  the  re- 
sulting shadow  and  to  minimize  its  distortion. 
To    still    further   increase    the    definition    and 


prevent  the  loss  of  detail,  which  results  from 
scattered  and  secondary  radiations,  it  becomes 
necessary  to  utilize  such  adjuvant  means  as 
diaphragms,  cones,  cylinders  and  the  Bucky 
diaphragm.  The  result  of  the  utilization  of 
all  these  factors  is  to  increase  the  exposure 
time. 


Fig.  ^85. — Automatic  time  switch  and  breaker 
(Wappler) 

The  exposure  may  be  timed  by  means  of 
metronome  or  an  automatic  timing  device. 

Where  instantaneous  exposures  are  made 
the  automatic  time  switch  is  to  be  preferred. 
This  usually  consists  of  a  timing  element 
and  a  mercury  circuit  breaker  interconnected. 
The  metronome  does  not  aid  in  the  control  of 
exposures  of  less  than  one  second. 

The  serial  timer  and  breaker  (\\'appler) 
consists  of  tv\'o  main  parts,  a  timing  device 
and  a  device  for  the  interruption  of  the  pri- 
mary current  of  the  transformer. 

The  timing  device  contains  an  air  bellows, 
which  has  an  escape  valve  that  can  be  regu- 
lated to  close  electric  contacts  for  the  various 
lengths  of  time.  Closing  the  circuit,  actuates 
an  electro-magnet,  the  armature  of  which 
carries  a  pair  of  copper  rods,  which  make  con- 
tact with  the  mercury  contained  in  two  sep- 
arate iron  pots. 

In  each  pot  is  placed  34  lb.  of  pure  mercury 
covered  with  oil  reaching  nearly  to  the  brim. 

The  timing  device  is  calibrated  for  periods 
extending  from  1/60  to  ten  seconds.  In  the 
dial  face  there  is  a  circular  hole  closed  with  a 


198 


THICKNESS  OF  PART 


piece  of  rubber,  which  gives  access  to  an 
adjusting  device.  After  removing  this  rubber, 
a  screw  becomes  visible  and  this  screw  is  to 
be  employed  to  make  corrections  for  improper 
timing. 

The  escape  valve  of  the  bellow  case  is  lo- 
cated behind  the  dial.  This  valve  may  become 
clogged  with  dust.  The  removal  of  the  dial 
gives  access  to  the  mechanism  for  the  purpose 
of  cleaning.  In  order  to  clean  this  slit,  it  is 
best  to  employ  a  strong  piece  of  paper  passing 
it  through  the  fine  slit  to  remove  all  dust  and 
dirt  that  might  have  accumulated  there. 

The  timer  and  magnet  of  the  breaker  are 
connected  in  series  across  the  current  inlet. 
The  mercury  breaker  is  connected  in  scries 
zvith  the  primary  of  the  transformer,  gen- 
erally in  parallel  with  the  operating  switch  of 
the  x-ray  circuit.  The  timer  is  operated  by 
two  strings.  One  sets  the  timing  device  and 
the  other  releases  it,  and  makes  the  exposure. 

Besides  the  factors  already  described,  two 
others  are  to  be  considered  in  the  estimation 
of  the  exposure : 

1.  Thickness  of  part 

2.  Sensitiveness  of  plate. 

The  Thickness  of  the  Part 

Numerous  tables,  giving  the  relation  of  the 
thickness  of  a  part  in  inches  to  the  exposure 
in  milliampere  seconds  with  a  ray  of  definite 
penetration  have  been  established.  Any  such 
table  must,  however,  be  used  with  great  dis- 
crimination, since  parts  of  the  same  thickness 
apparently  vary  in  their  opacity  to  the  same 
quality  of  ray,  because  of  variation  in  density. 
The  exposure  tables  have,  however,  a  great 
value  because  even  with  this  uncertain  factor, 
the  latitude  of  the  plate  is  sufficient  to  give  a 
useful  radiograph. 

Variations  in  time  for  various  thicknesses 
of  tissue  with  a  fine  focus  Coolidge  tube  carry- 
ing 20  milliamperes  backing  up  five  inches 
spark  at  a  distance  of  60  cm.  from  Seed 
plates  according  to  Kuegel  are  given  in  Table 
XV.^ 

The  thickness  of  the  part  and  the  distance 
from  target  to  plate  may  be  determined  with  a 


Thickness 
of  Part  Exposure 

CM, 

1 1  3    "^ 

2 1/2 

3 7/12 

4 3/4 

5 11/4 

6 13/4 

7 2  1/4 

8 3 

9 3  1/2 

10 5 

11 6  1/2 

12 8 

13 9 

14 10 

15 11 

16 12 

17 13  1/2 

18 15 

19 16  1/2 

20 18 

21 19  1/2 

22 21 

23  22 

2a\.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.  23  1/2 

25 25 

Table  XV 


fair  degree  of  accuracy  by  a  little  slide  ruler, 
devised  by  Bowen.  An  ordinary  yard  stick, 
^4  inch  wide  by  J4  inch  thick,  is  fitted  with 
trammel  points  such  as  are  used  for  the  ordin- 
ary beam  compass.  The  points  are  removed 
and  for  them  are  substituted  two  small  brass 
rods,  each  6  inches  long.  These  are  placed  on 
the  stick  so  that  one  points  in  one  direc- 
tion and  the  other  opposite ;  the  one  is  used 
to  measure  the  thickness  of  the  patient  and 
the  one  to  measure  the  distance  to  the  anode. 

Sensitiveness  of  Plate 

By  the  sensitiveness  is  meant  its  response 
to  the  radiation,  as  shown  in  chemical  changes 
made  manifest  by  development  in  the  black- 
ening of  the  plate.  This  blackening  is  pro- 
portional to  the  quantity  of  metallic  silver 
deposited  in  an  ailected  area  and  depends  as 
has  already  been  shown  on  the  quantity, 
quality  of  the  ray  and  on  the  time  and  distance 
of  exposure.  Therefore,  the  intensity,  quality 
and  distance  being  constant,  the  blackening 
produced  in  the  plate  increases  with  the  time 
of  exposure.  The  blackness  of  the  deposit  on 
the  plate  is  expressed  in  terms  of  density. 


SENSITIVENESS  OF  PLATE 


199 


This  density  is  judged  by  the  transinissibil- 
ity  of  light  or  its  inverse  opacity.  If  the  un- 
affected part  of  a  plate,  having  an  oj^acity  of 
zero,  transmits  a  certain  arbitrary  amount  of 
light.  100%,  an  area  transmitting  half  as 
much,  50%,  would  be  said  to  have  an  opacity 
of  2.  Thus  density  is  proportional  to  the 
amount  of  silver  reduced  per  unit  of  plate 
area.  The  plate,  which  gives  the  maximum 
density  for  the  same  unit  of  exposure  is  the 
plate  which  has  the  greatest  "speed."  The 
density  of  two  plates  may  be  the  same,  but 
the  chemical  change  throughout  the  emulsion 
may  not  be  similar. 

Contrast  depends  on  the  quality  of  the 
radiation.  It  diminishes  as  the  penetration 
of  the  ray  increases.  For  the  differentiation 
of  tissues  of  similar  density,  therefore,  rays 
of  low  penetration  must  be  used  while,  if  the 


Fig.  286 


the  density  increases  with  increase  of  develop- 
ment. "  Fogging  "  contributes  its  quota  to  the 
density  of  the  affected  emulsion  and  the  extent 
of  fogging  varies  with  the  particular  emulsion 
being  greater  where  the  concentration  of  silver 
in  the  gelatine  emulsion  is  hitrh.     The  shorter 


Fic.  287 

Sections  of  X-Ray   films  magnified  37S-D,   showing 
the   silver   particles.     (Hodgson) 

Fig.  286. — Density  of  1.5  impressed  by  light  from 
Fluorescent  Screen,  the  absorption  is  high  in 
the   surface  layers. 

Fig.  287. — Density  of  1.5  impressed  by  direct  X-rays, 
the  image  is  uniformly  distributed  through  the 
emulsion. 


the    exposure,    the    greater    the    tendency    to 
fogging. 

The  eft'ect  of  fog  is  to  blur  detail  and 
diminish  contrast.  Thus,  plates  having  great 
speed  have  a  greater  tendency  to  fogging, 
other  factors  of  development  being  the  same. 


absorptive  power  of  the  tissues  radiated  dift'ers 

considerably,  a  ray  of  high  penetration  would  Since  definition  and  contrast  are  more  impor- 

give  the  maximum,  rendering  power.  tant  than  speed  in  a  radiographic  plate,  these 

Contrast  also  depends  upon  the  degree  of  two  factors  should  receive  the  first  considera- 

development.    All  other  factors  kept  constant,  tion  in  the  choice  of  the  plate. 


CHAPTER  XIX 
EXPOSURE  TABLES 

Given  a  ray  of  proper  penetrative  quality 
for  the  outlining  of  the  particular  structure 
and  at  a  certain  target  plate  distance,  the  ex- 
posure should  be  directly  proportional  to  the 
milliamperage.  But  whether  the  exposure  is 
to  be  shortened  by  an  increase  of  milliamper- 
age or  the  milliamperage  diminished  with 
lengthened  exposure  will  depend  on  the  fac- 
tors already  cited. 

For  the  same  spark-gap  and  current  values 
the  same  exposure  time  is  recjuired  when  using 
the  Coolidge  tube  as  when  using  the  gas  tube. 

The  time  for  proper  exposure  does  not 
follow  the  law  of  absorption  because  of  scat- 
tering and  secondary  radiations.  There  is  no 
virtue  in  intermittent  exposures,  the  interval 
is  usually  too  short  to  overcome  the  tendency 
to  voltage  drop  from  heating  in  gas  tubes.  In 
Coolidge  tube  the  procedure  is  particularly 
of  no  avail. 

Method  A. 

Melthorpe  has  suggested  that  an  exposure 
table  may  be  arranged  to  serve  under  condi- 
tions where  a  tube  of  average  hardness  must 
be  used  for  the  different  parts  of  the  body 
and  when  an  average  negative  must  suffice  as 
in  work  in  the  field,  by  the  use  of  the  follow- 
ing formula : 


T 


KD' 


H-C 


T=Time  measured  in  seconds. 

D^Distance  measured  in  centimeters. 

H^Hardness  measured  in  Benoist  units. 

C^^Current  measured  in  milliamperes. 

K=Factor  whose  value  will  vary  with  the 
thickness  of  the  object  between  the  target  and 
the  plate  and  with  its  absorption  coefficient. 


A  series  of  factorial  values  has  therefore 
been  arranged  for  the  various  parts : 

Part  of  Body  K 

Head   (A-P) 3.3 

Kidney    region    3.0 

Lumbar    vertebrae     3.0 

Lower    dorsal    vertebrae 3.0 

Head    (lat)     2.8 

Pelvis     2.6 

Hip   joint    2.1 

Chest    i.S 

Shoulder    1.2 

Thigh    1.2 

Knee     0.9 

Upper    arm     0.7 

Tarsus   (A-P)    0.7 

Leg    0.4 

Foot    0.3 

Forearm   0.2 

Hand    0.15 

T.^BLE    XVI 

If  the  exposure  time  for  a  pelvis  is  required 
at  a  target  plate  distance  of  50  cm.  (20  in- 
ches), with  a  5  Benoist  ray  (about  5  inch 
gap),  with  a  current  of  40  milliamperes,  the 
formula  would  read 

2.6  X  (50)  = 

T  = =  6.5  seconds 

5^x40 

Method  B. 

With  57,500  volts  (effective)  and  10  milli- 
amperes and  a  distance  of  45.7  cm.  (18  in.) 
from  focal  spot  to  plate,  Coolidge  and  Moore 
have  found  that  for  Seed  plates  and  the  aver- 
age adult  subject,  the  following  table  of  ex- 
posures gives  good  average  results : 

Exposures  18  in.  distance.  Sec. 

Hand    1 

-  Elbow    2 

Ankle    2 

Knee    4 

Shoulder   8 

Chest   10 

Hip    20 

Head-lateral    25 

Frontal   sinus    50 

Table  XVH 


[200] 


EXPOSURE  TABLES 


201 


Method  C. 

An  exposure  table  constructed  on  the  basis 
of  the  relationship  of  the  thickness  of  the  part 
to  the  unit  of  radiation  necessary  to  outline 
the  part  in  its  proper  density  and  contrast  has 
been  suggested  by  ^V.  W.  Mowry.  In  the 
table  below  the  units  of  radiation  are  placed 
in  columns  for  Seed,  Diagnostic  and  Dupli- 
tized  films  and  for  d.  c.  and  a.  c.  machines. 


Working  Formula 

R  =  CXV-XT 
D= 

R  =  Units  of  radiation  needed  for  certairt 
thickness  of  part. 

C  =  Current  in  milliani])eres  flowing 
through  tube. 

V-  ^  Square    of    voltage    as    measured    in 


Units  of  Radiation  Necessary  for  Standard  Depths  and  Standard  Plates  (Mowry) 


Alternating  Current  Machines 

Direct  Current  Machines 

Depth  Inches 

Radiation 
Seed  Pits. 

Radiation 

Dia,£fnostic 

Plates 

Radiation 

Duplitized 

Films 

Radiation 
Seed  Pits. 

Radiation 

Diagnostic 

Plates 

Radiation 

Duplitized 

Films 

1   

.18 
.40 
.70 
1.15 
1.65 
2.20 
3.00 
3.65 
4.55 
5.50 
6.50 
7.65 
8.85 

10.00 

11.5 

13. 

14.5 

16.3 

18. 

20. 

22. 

24. 

26. 

.13 

.30 

.50 

.85 

1.20 

1.65 

2.15 

2.65 

3.35 

4.02 

4.80 

5.65 

6.50 

7.50 

8,50 

9.55 

10.75 

12,00 

13.3 

14  65 

16.1 

17  55 

19.15 

.1 
.25 
.4 
.63 
.9 
1.25 
1.60 
2.0 
2.5 
3,05 
3.5 
4.25 
5,0 
5.65 
6.4 
7.25 
8.1 
9, 
10. 
11. 
12. 
13.25 
14.4 

.24 
.55 
.95 
1.5 
2,15 
2.95 
3.85 
4.85 
6. 

7.25 
8,65 
10,2 
11,8 
13.5 
15.4 
17.4 
19.5 
21.7 
24.1 
26.5 
29.2 
31.8 
34.7 

.177 
.398 
.70 
1.11 
1,6 
2.2 
2.85 
3.6 
4.45 
5.35 
6,35 
7,5 
8,7 
9,95 

11.35 

12.8 

14.3 

15.95 

17.7 

19.5 

21.4 

23.3 

25.5 

.13 
.3  , 
.5 
.85 
1.2 
1.65 
2.15 
2.65 
3.35 
4.02 
4.8 
5,65 
6,50 
7.50 
8.50 
9.55 
10.75 
12. 
13.3 
14.65 
16.1 
17.55 
19.55 

If 

2  

2J 

3  

3| 

4 

4i 

5  

5| 

6  

61 

7 

8i 

9  

9i 

10  

lOi 

n" 

Ill 

12  

TABLE  XVIII 


The  above  table  indicates  the  units  of  radia- 
tion necessary  for  different  thicknesses  of 
tissue,  measured  in  inches  along  the  line  of  the 
central  ray.  For  intensifying  screen  work  and 
roentgenograms  of  the  frontal  sinus,  teeth, 
chest  and  kidney  under  compression,  the 
above  units  cannot  be  applied  directly  but 
simple  multiples  of  same  should  be  used. 

To  this  end,  conversion  factors  are  utilized 
in  examinations  of  the  head  and  chest.  In  the 
head  the  factor  is  1.7;  for  the  chest  it  is  .25. 


inches  of  spark  gap  by  flame  tests  between 
blunt  points,  employing  quarter  second  flashes. 

D-  =  Scjuare  of  the  distance  in  inches. 

Radiographic  results,  giving  best  contrast 
are  obtained  when  the  intensity  of  x-rays  is 
just  sufficient  to  penetrate  the  part  in  ques- 
tion. The  practical  limits  of  penetration  are 
three  to  seven  inches  spark  gap. 

To  avoid  the  danger  of  burning  the  follow- 
ing practical  rule  should  be  observed : 

The   thickness  of  the  part   in   inches   must 


202 


EXPOSURE  TABLES 


not  exceed  Ij/  to  2  times  the  spark-gap  used. 
For  example,  a  three  inch  gap  should  not  be 
employed  for  radiographing  any  part  exceed- 
ing in  thickness  Ij^   x  3",  or  4j4".    The  prac- 


tical limit  for  a  4"  penetration  would  be  6" 
part,  etc. 

Example.     To  find  the  time  of  exposS're  of 
a  knee  measurinsr  4"  in  thickness  in  the  lateral 


EXPOSURE  TABLE  BASED  ON  A  VARYING  PENETRATION  ACCORDING  TO  THE  THICKNESS 
OF  THE  PART.      SEED  PLATES  D.  C.  MACHINE. 


Part 

Depth 

Dist. 

Sp.  Gap 

Mills. 

Time 

Part 

Depth 

Dist. 

Sp.  Gap 

Mills 

Time 

low   LowcT 

4' 
41" 

24' 
24' 

5' 

5" 

40 
40 

2.2 
3.0 

Ankle 

2" 

2-5' 

20' 
20' 

3' 
3' 

50 
50 

.9 

1.3 

5" 

24" 

5" 

40 

3.4 

3" 

20' 

3" 

50 

2.0 

5J" 

24" 

5" 

40 

4i 

34" 

20' 

3' 

50 

2.6 

6- 

24" 

5' 

40 

5.0 

4" 

20' 

3' 

50 

3.5 

&V 

24' 

5' 

40 

5.8 

44" 

20' 

4' 

40 

3.0 

T 

24' 

5" 

40 

6} 

5" 

20' 

4" 

40 

3.7 

spine    Cenncal.      A.    P.    & 

4" 

44- 

5' 

20" 
20" 

3" 

4' 
4' 

50 
40 

3.5 
3.0 
3.7 

Foot, 

See 

Hand  & 

Wrist 

Lateral 

20" 

40 

Kidneys,  Ureters  and  Blad- 

4" 

20' 

3' 

50 

3.5 

5i" 
6" 

20" 
20" 

4' 
5' 

40 
40 

4.5 
3.5 

der  

4-5" 
5" 

20' 
20' 

4' 
4' 

40 
40 

3.0 

3.7 

6-5" 

20' 

5" 

40 

4.0 

54' 

20' 

4- 

40 

4.5 

7" 

20' 

5' 

40 

4.7 

6' 

20" 

4' 

40 

5.4 

64' 

7" 
7h' 

20" 
20" 
20' 

4' 
5' 
5' 

40 
40 
40 

6.3 

4.7 

DoTsal.     Spine 

6" 
64" 

20' 
20" 

.       5" 
5' 

40 
40 

3.5 
4.0 

5.4 

7' 

20" 

6" 

35 

3.7 

8" 

20" 

5' 

40 

6.1 

IV 

20" 

6' 

35 

4.3 

8-5" 

20" 

54' 

35 

5i 

8" 

20' 

6' 

35 

5.0 

9' 

20" 

54" 

35 

6.4 

8J" 

20' 

6' 

35 

5i 

94" 

20' 

6' 

35 

7.0 

9" 

20' 

7' 

35 

4-5 

10" 

22" 

6' 

35 

9.2 

9r' 

20' 

1 " 

35 

5.0 

105" 

22" 

7" 

35 

7.5 

10" 

20' 

1" 

35 

5.6 

11' 

22" 

7" 

35 

8i 

lOJ" 

20' 

7" 

35 

6.2 

114' 

22' 

7" 

35 

9.0 

11' 

20' 

7" 

35 

6.8 

12' 

22' 

T 

35 

9i 

lU' 
12" 

20' 
20' 

rrl    It 

35 
35 

6.5 
7.0 

1  ^ 

7-r 

Hand 

V 
1" 

20' 
20' 

3' 
3" 

50 
50 

1 

1 

Lumbar  Spine.  Sacrum.  & 

4" 

4i" 

5' 

20' 
20' 
20' 

3' 

4" 
4' 

50 
40 
40 

3.5 
3.0 
3.7 

14" 

20" 

3" 

50 

1 

Sacro-Iliac 

Wrist.  Ant.  P.  and  Forearm 

IV 

20" 

3" 

50 

4 

5-5" 

20" 

4" 

40 

4.5 

2" 

20" 

3" 

50 

.9 

6" 

20" 

5" 

40 

3.5 

24" 

20' 

3" 

50 

1.3 

64" 

20" 

5' 

40 

4.0 

3' 

20' 

3" 

50 

2.0 

7" 

20" 
20" 

5" 
5' 

40 
40 

4.7 
5.4 

Wrist,  Lateral 

2V 

20' 

3" 

50 

1.3 

8" 

20" 

5' 

40 

6.1 

3" 

20' 

3' 

50 

2.0 

8i' 

20" 

■5-1 " 

35 

55 

34" 

20' 

3" 

50 

2.6 

9' 

20" 

5V 

35 

6  4 

4' 

20' 

3' 

50 

3.5 

94" 
10" 
lot" 

20" 
22" 
22" 

6' 
6' 

T 

35 
35 
35 

7.0 
9.2 

7i 

Elbow  A.  P 

24" 
3' 

20' 
20' 

3' 
3' 

50 
50 

1.3 

2.0 

11" 

22" 

T 

35 

8i 

34' 

20" 

3" 

50 

2.6 

lU" 

22" 

T 

35 

9.0 

4' 

20' 

3" 

50 

3.5 

12" 

22' 

T 

35 

9J 

PI  how    T  ateral 

3' 
35-' 

20' 
20' 

3" 
3' 

50 
50 

2  0 

Pelvis.   Coccyn   &  Pubes. 

=same 

as 

Lumbar 

Spine. 

'    .'  U\J  VV,     X<£1L^1C11........... 

2.6 

4' 

44' 

5' 

20' 

3" 

50 

3  5 

JHip  &  Femur. . .- 

4' 
44" 

20' 
20' 

4' 
4' 

40 
40 

2.4 
3.0 

20' 
20" 

4' 
4' 

40 
40 

sio 

3.7 

5' 
Si" 

20' 
20' 

4" 
4' 

40 
40 

3.7 
4.5 

Shoulder  and  Humerus 

3" 

20" 

3' 

50 

2.0 

6" 

20' 

5" 

40 

3.5 

34" 

20' 

3" 

50 

2.6 

6i" 

20' 

5" 

40 

4.0 

4" 

20" 

3" 

50 

3.5 

7" 

20' 

5" 

40 

4.7 

44" 

20' 

4' 

40 

3.0 

74" 

20" 

5' 

40 

5.4 

5' 

20' 

4' 

40 

3.7 

8" 

20' 

5" 

40 

6.1 

54' 

20' 

4" 

40 

4.5 

8i" 

20" 

6" 

35 

5* 

6" 

20' 

5' 

40 

3.5 

9" 

20' 

6' 

35 

6.2 

64' 

20' 

5' 

40 

4.0 

94' 
10" 

20' 
22' 

6" 
6' 

35 
35 

7.0 
9.2 

Head  A.  P.  and  Sinuses. . . 

5" 

20' 

6' 

35 

3i 

54' 
6" 

20' 

6' 

35 

4  0 

Knee  &  Tibia  &  Fibula.... 

3' 

20' 

3" 

50 

2.0 

20' 

6' 

35 

4} 

34' 

20' 

3" 

50 

2.6 

64" 

20' 

6' 

35 

54 

4" 

20' 

3" 

50 

3.5 

7" 

20' 

6" 

35 

6.3 

4i' 

20' 

4' 

40 

3.0 

74' 

20' 

6" 

35 

7.2 

5' 

20' 

4' 

40 

3.7 

8' 

20' 

6' 

35 

8.2 

54" 

6" 

64" 

20' 
20' 
20 

4" 
5' 
5 

40 
40 
40 

4.5 
3.5 
4.0 

Lateral 

5' 
54' 

20' 
20" 

5' 
5' 

40 
40 

4.0 

5.0 

7" 

20" 

5' 

40 

4.7 

6' 

ir 

20' 
20' 
20' 
20' 
20' 

5' 
6' 
6' 
6' 
6' 

40 
35 
35 
35 
35 

5J 

54 

6.3 

7.2 

8.2 

Table  XIX 


EXPOSURE  TABLES 


203 


posture,  using  Seed  plates  and  a  standard  type 
of  alternating  current  interrupterless  machine, 
with  a  current  of  50  millianiperes  and  a  4" 
gap,  and  a  20"  target-plate  distance. 

The  formula  being  applied,  the  following 
results  are  obtained :  The  unit  of  radiation  in 
column  2  of  table  XVIII  (alternating  current 
machine;  Seed  plates)  opposite  the  four  inch 
thickness  is  3. 

3  =  50  X  16  X  T 


400 
1200  =  50  X  16  XT 
^   1200 


800 

12 

"8" 

T  =  1 1/,  sec. 


T 


Screen  work  depends  directly  upon  the 
intensification  factor.  Certain  screens  reduce 
exposure  time  to  1/5  normal  time,  so  that  the 
radiation  needed  with  such  screens  is  1/5  of 
the  time  designated  in  the  table  for  the  de- 
sired part. 

When  employing  plate  changers  and  tun- 
nels, the  absorption  of  the  aluminum  holders 
must  be  accounted  for;  fifty  per  cent  increase 
in  exposure  time  may  be  required. 

Exceptions 

According  to  the  table,  the  unit  of  radiation 
indicated  for  8"  thickness  is  11.5.  If  it  is  a 
head  however,  which  is  to  be  radiographed  in 
the  posterio-anterior  or  antero-posterior  posi- 
tion, a  conversion  factor  must  be  used.  This 
is  1.7  for  such  head  examinations;  1.7  multi- 
plied by  11.5  gives  19.55  units.  (For  examina- 
tion of  the  head  laterally  the  general  rule  is 
followed  without  the  conversion  factor.) 

For  chest  examination  the  units  of  radiation 
of  the  table  must  be  multiplied  by  the  conver- 
sion factor  .25.  Thus  the  unit  of  radiation 
for  an  8"  chest  would  be  .25  x  11.5  or  2.87. 

\\'here  compression  is  used  the  depth  is 
measured  from  the  curvature  of  compression 
medium,  to  the  plate  and  along  the  line  of  the 
central  ray.     If  an  inflated  bag  be  employed. 


no  correction  is  needed.  If  aluminum  com- 
pression is  used,  it  is  often  necessary  to  in- 
crease exposure  time  50  per  cent,  the  increase 
depending  upon  the  thickness  of  the  aluminum 
cap  which  may  be  readily  computed  after  a 
few  exposiu'es. 

With  Coolidge  as  with  gas  technique  it  is 
neither  advisable  nor  possible  to  utilize  one 
tube  for  every  variety  of  work.  The  best 
practice  is  to  use  sharp  focus  tubes  for  all 
work  excepting  for  the  gastro-intestinal  tract 
examinations.  Though  it  is  conceded  that 
with  large  energy  input  such  as  becomes  nec- 
essary for  chest  work,  the  focus  does  not 
remain  sharp  for  long,  still,  if  the  given  tube 
is  used  for  chest  work  only,  the  focus  will  be 
as  small  as  can  be  maintained. 

When  a  large  number  of  examinations  are 
made  it  is  advisable  to  have  a  ditt'erent  Cool- 
idge tube  for  extremity,  for  kidney,  for  chest 
and  for  gastro-intestinal  work. 

Method  D. 

By  the  use  of  voltages  equivalent  to  4,  5 
and  6  inches  spark  gap  and  milliamperage 
values  of  30,  40,  55,  100  and  110,  exposure 
tables  may  be  constructed.  (See  Tables  XX, 
XXI,  and  XXII.) 

The  size  of  parts  in  inches  is  estimated  when 
the  part  is  in  position  for  examination.  The 
thickness  of  the  trunk  for  kidney  examination 
is  measured  at  a  point  half  way  between  the 
umbilicus  and  lower  end  of  the  sternum,  for 
the  gall  bladder  examination  at  the  level  of  the 
umbilicus,  for  chest  examination  at  the  level  of 
the  nipple  line,  for  hips  at  the  level  of  the  an- 
terior superior  spine. 

The  maintenance  of  a  target-skin  distance 
of  eighteen  inches  is  not  always  possible  if 
the  various  length  cones  are  used.  The 
numerals  under  the  heading  cone  indicate  the 
diameter  of  the  cone  at  its  wide  end. 

^^'here  speed  is  necessary,  this  may  be  ob- 
tained by  increasing  the  milliamperage. 
Doubling  the  milliamperage,  halves  the  time. 

Doubling  the  gap  cuts  the  time  by  four. 

Infant  yj  of  the  regular  exposure. 


204 


EXPOSURE  TABLES 


EXPOSURE  TABLES 

WaPPLER  iNTERRXJPTERLESb  KiNG  MODEL  220  D.  C.^  7  1/2  K.  W. 

Gas  Tl'ee 


PART 


PLATE 


TUBE 

IND.  4 

TEST 

RHEO. 

7 

12 

7 

12 

7 

12 

8 

15 

7  1/2 

12 

8 

15 

8 

15 

7 

12 

7 

12 

7 

15 

7 

12 

8 

15 

8 

15 

8 

15 

8 

15 

8 

15 

8  1/2 

15 

8 

15 

8 

15 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

8 

18 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

8  1/2 

15 

9 

18 

9 

18 

8  1/2 

12 

8 

12 

8 

12 

7  1/2 

18 

7  1/2 

18 

7  1/2 

18 

EXPOSURE    TIME  (Seconds) 
Thin  Med.  Thick      Very  Thick 


Whole  Head-lat 

Whole  Head-post,  ant 

Mastoid  lat.-obl 

Lower  jaw-obl 

Teeth 

Spine  cervical-post 

Spine  cervical-lat 

Spine  dorsal-post 

Spine-dorsal-lat 

Spine-luinbar-post 

Spine-lumbar-lat 

Sacrum-post 

Coccyx-post 

Pelvis-post 

Pubis-ant 

Hip-post 

Femoral  shaft 

Knee-ant 

Knee-lat 

Tibia 

Ankle-post 

Ankle-lat 

Ankle-oblique 

Foot-plantar 

Foot-lateral 

Shoulder-post 

Arm 

Elbow 

Forearm-prone 

Forearm-lat 

Hand-prone 

Chest  post,  and  ant 

Chest  oblique 

Kidneys  post 

Bladder 

Gall  bladder-ant  \jj 

Stomach-ant       (  

.Colon-ant.  and  postl 

Esophagus-obliquef^™: 


10x12 

8x10 

5x    7 

8x10 

Fihn 

8x10 

8x10 

11x14 

11  x  14 

10x12 

11  X  14 

10x12 

10x12 

14x17 

10x12 

8x10 

11x14 

8x10 

8x10 

10x12 

8x  10 

8x10 

8x10 

5x    7 

5x    7 

8x10 

10x12 

8x10 

8x10 

8x10 

5x    7 

14x17 

14x17 

10x12 

10x12 

8x10 

14  x  17 

14x17 

14x17 


1/2 


1/2 
3/4 
1/2 
1/2 


7/8 
7/8 
7/8 
7/8 
1/4 

3/4 

2/3 

2/3 

1/2 

1/3 

1/2 

1/3 

1/3 

7/8 

1/3 

1/3 

1/4 

2/5 

1/6 

4/10 

3/4 


1/12 
1/20 
1/20 
1/40 


1/5 
3/4 


2  1/4 
1  1/2 
10 


1  1/4 

1  1/4 

1  1/4 

1  1/4 

1  1/2 

1  1/8 

7/8 

3/4 

3/4 

2/3 

1/2 

2/3 

1/2 

1/2 

1 

1/2 
1/2 
1/3 
1/2 
1/5 
1/2 
1 
3  1/2 
3  1/2 
1/10 
1/16 
1/16 
1/40 


5 
5 
5 
2 

1 

1 

2 

3 

2 

12 

2 

2 

2 

2 

2 

1 

1 


1/4 
1/4 
1/2 
1/4 
1/5 
1/4 

1/2 


1/4 
1/4 


1 


7/8 
7/8 
3/4 
2/3 
3/4 
2/3 
2/3 
1/4 
2/3 
2/3 
1/2 
2/3 
1/4 
2/3 

1  1/2 

5 

5 
1/4 
1/10 
1/10 
1/3U 


1/2 


1/2 
1/5 
1/2 
1/4 


1 

1 

6 

3 

3 

15 

2  3/4 

"  3/4 
3/4 
3/4 


1/2 
1/4. 


7/8 
3/4 
7/8 
3/4 
3/4 
1/2 
3/4 
3/4 
2/3 
3/4 
1/3 
3/4 


1/2 
1/5 
1/5 
1/20 


T.ABLE    XX 


Exposures  given  in  the  above  table  are  for 
Seed  plates. 


Tube  Test 

Button 

Spark-gap 

Milliamperes 

7 

12 

5  1/4 

45 

15 

5  1/2 

55 

8 

12 

4  1/4 

60 

15 

4  1/2 

70 

12 

3  1/2 

75 

9 

15 

4 

100 

18 

4  3/4 

120 

Table    XXI 


HAi  VJ:5Uis.r;,    \ /\oi^rL^ 


^VD 


CooLiDGE  Tube 


CooLiDGE  Tube 


V 

S 

S 

a 

^ 

a 

Ti 

VIE 

*J 

a 

^ 

s 

3 

— 

a 

Time 

*J 

£ 

m 

Q 

o= 

1 

i 

O 

Parag 

Seed 

1 

N 

in 

a 

d 

s. 

1 

CO 

0 

Parag 

Seed 

Head 

Thin 

20 

3 

S 

30 

6 

5 

8  1/3 
10  2/3 
12     ' 

Knee 

Thin 

21 

5 

s 

55 

4 

2  3/4 

3  2/3 

Sinus 

Medium 

6 

Medium 

3  1/4 

4  1/3 

Stout 

7 

Stout 

3  3/4 

4  1/4 

5  2/3 

Head 

Thin 

22 

9 

S 

40 

5 

3 

|V3 

Lateral 

Medium 

4 

Leg 

Thin 

21 

s 

55 

4 

2 

3V3 

Stout 

5 

6  2/3 

Medium 

3 

Stout 

3  1/2 

4  2/3 

Head 

Thin 

19 

3 

s 

40 

5 

4 

5  1/3 

5  1/2 

Mastoids 

Medium 

4  3/4 

5  172 

6  1/3 

Stout 

7  1/2 

Ankle 

Thin 

20 

5 

s 

55 

4 

1 

2  2/3 

Medium 

1   1/2 

3  1/3 

Head 

Thin 

24 

5 

S 

30 

6 

4  1/2 

Stout 

2    ■ 

4     ' 

Base 

Medium 
Stout 

5     ' 
5  1/2 

2  1/2 

4   2/3 

Foot 

Thin 

20 

5 

s 

55 

4 

1 

3 

Mandible 

Thin 

Medium 

Stout 

5 

s 

55 

4 

3  1/4 
3  1/2 
4 

|2/3 
6  1/3 

Medium 
Stout 

1   1/4 
1   1/2 

3  1/3 
3  2/3 
4 

Spine 

Thin 

20 

5 

S 

55 

4 

2 

2  2/3 

Teeth 

Thin 

12 

3 

s 

55 

4 

2   §4 

Cervical 

Medium 
Stout 

2  1/4 
2  1/2 

3    ' 

3  1/3 

Sfernum 

Medium 
Stout 

22 

9 

s 

55 

5 

2 
3 

4 

Spine 

5  1/2 

20 

9 

s 

40 

5 

1   1/3 

1  2/3 

Dorsal 

6    ' 

6  1/2 

7  ' 

1  1/2 
2 

2  1/4 
2  1/2 

2    ' 
2  2/3 
3 

Chest 

6 

6  1/2 

7  ' 

26 

M 

no 

5 

1/4 
1/3 
2/5 

7  1/2 

3  1/3 

7  1/2 

11^ 

8 

3 

4 

8 

ZiS 

8  1/2 

3  1/2 

4  2/3 

8  1/2 

ti 

9 

4 

5  1/3 

9 

7/8 

10 

5 

6  2/3 

10 

1 

11 

6 

8 

11 

1/2 

12 

7 

9  1/2 

12 

2 

Spine 

Thin 

22 

9 

s 

40 

5 

4 

5   1/3 

Chest 

fi 

26 

M 

110 

5 

1/15 

Dorsal 

Medium 

5 

6  2/3 

(■screen) 

6  1/2 

1/14 

Oblique 

Stout 

6 

8     ' 

7  1/2 

1/12 
1/11 

Spine 
Lumbar 

Thin 

Medium 

Stout 

22 

3 

s 

40 

5 

4 
5 
6 

5  1/3 

6  2/3 

8    ' 

8  1,  2 

9  ' 
10 

1/10 

1/8 
l'/6 
1/5 

Shoulder 

Thin 

Medium 

Stout 

21 

5 

s 

40 

5 

3 

3  1/4 

4 

4  1/3 

5  2/3 

11 
12 

174 
3/ '10 

Arm 

Thin 

20 

9 

s 

55 

4 

1 

2  2/3 

Heart 

Adult 

Medium 

1  1/4 

3    ' 

(screen) 

Thin 

80 

M 

110 

5 

1/6 

Stout 

2    ' 

3  1/3 

Medium 
Stout 

1/5 
1/3 

Elbow 

Thin 

20 

3 

s 

55 

4 

1 

2  1/3 

Medium 

2 

2  2/3 

Esophagus 

Stout 

2  1/4 

3    ' 

(screen) 

Thin 
Medium 

26 

M 

110 

5 

1/10 
1/8 

Forearm 

Thin 

20 

5 

s 

55 

4 

1  1/2 

2 

Stout 

1/6 

Medium 

1  3/4 

2  1/3 

Stout 

1/4 

Stout 

2 

2  2/3 

Stomach 

5 

27 

M 

100 

6 

1/12 

Colon 

5  1/2 

1/11 

Hand 

Thin 

20 

5 

s 

55 

4 

1 

1   1/3 

(screen) 

1/10 

Medium 

1  1/2 

1  2/3 

6  1/2 

1/8 

Stout 

1  1/3 
1  1/2 

1  3/4 

2  ' 

7  1/2 
S    ' 

8  1/2 

1/6 
1/5 
1/6 
1/5 

Pelvis 

5 

24 

9 

s 

40 

5 

4  1/2 

6 

9 

1/4 

Entire 

5  1/2 

6  ' 

6  1/2 

7  ' 

4  3/4 

5  1/4 
5  1'2 

6  1/3 

6  2/3 
7 

7  1/3 

10 
11 
12 

1/4 
1/3 
1/3 

7  1/2 

5  3/4 

7  2/3 

Call 

5 

18 

4 

S 

110 

5 

1/10 

8    ' 

6    ' 

8 

Bladder 

5  1/2 

1/8 

8  1/2 

6  1/4 

8  1/3 

("screen) 

6    ■ 

1/6 

9    ' 

6  1/2 

8  2/3 

6  1/2 

7  ' 

1/5 

10 

7 

9  1/3 

1/4 

11 

7  1/2 

10 

7  1/2 

8  ' 

3/10 

12 

8 

10  2/3 

'1/3 

|V2 

2/5 
1/2 

Hips 

5 

5  1/2 
6 

6  ]/2 

18 

5 

s 

40 

5 

4  1/2 
5 

5  1/2 
6 

6 

6  2/3 

7  1/3 
S 

10 
11 
12 

2/3 
,3/4 

7 

6  1/2 

8  2/3 

Kidneys 

5 

18 

9 

S 

55 

5 

4  2/3 

3  1/2 

7  1/2 

7 

9   1/3 

5  1/2 

6  ' 

5 

3  3/4 

8 

7   1/2 

10 

5  1/3 

8  1/2 

8 

10  1/3 

6  1/2 

6 

4  1/2 

9 

8  1/2 

12 

7    ' 

fi  2/3 

5    ' 

10 

9 

13  1/3 

71/2 
8  1/2 

7 
8 
8  2/3 

5  1/2 
6 

6  1/2 

7  ' 

Thigh 

Thin    ■ 

22 

s 

55 

4 

3  1/2 

4  2/3 

9    ' 

9  1/3 

Medium 

4     ' 

5  1/3 

10 

10    ' 

7  1/2 

St-ut 

4   1/2 

6    ' 

11 

11  3/4 

8  1/2 

9  1/2 

6  1/3 

12 

1 

12  2/3 

Table  XXII 


206 


EXPOSURE  TABLES 


Children  -/i  of  the  regular  exposure. 

Where  parts  are  encased  in  plaster  of  paris, 
double  the  exposure. 

A  continual  increase  in  the  time  of  exposure 
becomes  necessary  as  the  tubes  grow  older. 
This  is  due  to  the  metallic  deposit  thrown  on 
the  tube  wall  during  the  exposures,  the  de- 
posit acting  as  a  filter.  This  increase  is  most 
marked  during  the  early  stages  of  use.  When 
the  tube  gets  fairly  old,  the  increase  in  time  is 
not  so  rapid.  Tubes  used  with  very  low  gaps 
do  not  blacken  so  rapidly  as  those  with  higher 
gaps,  and,  incidentally,  the  increase  of  ex- 
posure time  is  not  necessary  so  frequently. 

An  important  consideration  in  exposure  is 
the  avoidance  of  a  skin  reaction  as  a  result  of 
too  prolonged,  too  many  or  improperly  ar- 
ranged exposures. 

The   dose,    as   has    alreadv   been    indicated, 


increases  with  the  time,  current  and  voltage 
(spark-gap)  and  diminishes  as  the  target  skin 
distance  increases.  The  interposition  of  an 
aluminum  filter,  though  an  essential  in  fluoro- 
scopy, is  not  necessary  in  radiography  be- 
cause our  modern  technique  is  instantaneous 
and  with  a  iive  inch  gap  voltage  at  a 
twenty  inch  target  skin  distance  forty-five 
milliampere  minutes  exposure  is  allowable. 
If  forty-five  milliamperes  are  used,  one  min- 
ute's exposure  is  the  limit  of  safety.  Thus 
four  exposures  over  the  same  area  of  fifteen 
seconds  each  with  forty-five  milliamperes  and 
a  five  inch  gap  would  be  dangerous.  If  a 
filter  of  aluminum  one  millimeter  in  thickness 
is  used  the  limit  is  increased  about  forty  per 
cent,  namely  to  sixty  milliampere  minutes. 
The  possibility  of  skin  reaction  is  greater  with 
lower  gaps  than  with  higher. 


CHAPTER  XX 

THE  DEVELOPMENT  OF  THE  PLATE 

The  Photographic  Dark  Room 

Since  the  manipulation  within  this  room 
plays  an  important  part  in  the  character  of  the 
radiograph  produced,  the  selection  of  the  room 
and  the  technique  of  developing  are  deserving 
of  careful  consideration. 

The  dark  room  should  fulfill  the  following 
specifications : 

L  It  should  be  of  ample  size.  It  is  as  much 
an  error  to  make  the  room  too  large  as  it  is 
to  make  it  too  small.  It  should  preferably 
be  at  least  eight  feet  wide  by  twice  this  in 
length.  No  open  shelving  should  exist. 
It  should  contain  sufficient  closet  space 
for  the  keeping  of  supplies  and  all  closets 
should  have  sliding  doors.  These  should  be 
disposed  on  one  side  of  the  room.  The  tables, 
tanks  and  so  forth,  utilized  for  developing, 
should  be  on  the  other  side  of  the  room  and 
preferably  made  of  Alberene  stone.  Thus  to 
the  left,  there  should  be  a  top  capable  of  sup- 
porting a  tray  rocker,  holding  an  eighteen  by 
twenty-two  inch  tray.  Next  to  this  a  sink 
(20  X  24)  with  hot  and  cold  water  faucets. 
Next  to  this,  a  tank  hypo  and  for  washing 
plates,  and  beyond  this,  a  top  for  holding 
drying  racks,  upon  which  suitably  disposed, 
a  fan  may  play.  Thus  the  various  manipula- 
tions may  be  carried  on  successively  by  work- 
ing in  one  direction.      (Fig.  290). 

2.  It  should  be  light-proof.  The  walls 
should  be  of  such  color  as  to  prevent  the  re- 
flection of  any  white  light,  which  may  enter. 
It  is  no  advantage  to  paint  the  walls  black. 
Red  or  orange  is  best  suited  for  the  purpose. 

3.  It  should  be  illuminated  with  a  safe  but 
sufficiently  bright  light.  Indirect  illumination 
in  a  bowl  with  a  tipless  ground  glass  ruby  bulb 
against  a  red  ceiling  gives  good  results.  A 
small  ruby  lamp  mounted  in  a  box  with  a  red 
and  yellow  filter  may  be  necessary  over  the 


tray,  in  which  the  development  is  done.  This 
should  however  be  at  least  4  feet  from  the 
tray. 

4.  It  should  be  well  ventilated.  This  may 
be  accomplished  by  many  of  the  special  ven- 
tilators, which  admit  air  but  no  light.  It  is 
important  to  keep  the  air  in  constant  motion 
by  fans.  It  is  by  this  movement  of  the  air 
that  the  ill  effects  may  be  avoided. 

The  Developixg  Solution  is  Prepared 

This  should  be  prepared  with  a  view  to- 
wards the  attainment  of  the  following  qualities. 

It  should  bring  out  all  detail  and  give  the: 
required  contrast. 

It  should  not  cause  fogging. 

It  should  not  give  too  rapid  development.. 

It  should  have  keeping  ciualities. 

Developing    Solutions 
These  consist  of  an 

1.  Active  oxidizing  agent. 

2.  Alkali. 

3.  Preservative. 

4.  Restrainer. 

The  developing  agents  are  of  two  varieties : 
organic,  as  hydrochinon,  and  inorganic,  as 
iron  oxalate.  The  organic  developing  agents 
are  nearly  all  derived  from  paramido-phenol, 
which  is  the  base.  Benzol  CgHg  is  converted 
into  phenol,  C,,H.-  OH,  and  this  successively 
becomes  paranitrophenol.  CcH^  OH.  NO,  and 
paramidophenol,  QH^  OH.  N.  H^.  The  mod- 
ern developers  are  derivatives  of  this  base. 
The  capabilities  of  the  paramidophenol  itself, 
as  a  reducing  agent  for  photographic  work  is 
equal  practically  to  metol,  hydroquinone, 
glycin,  orthol  or  eikonogen. 

By  using  the  reducing  agent  in  solutions  of 
various  concentrations  and  with  different  pro- 
portions of  accelerator  and  restrainer,  with 
various  test  negatives,  it  is  possible  to  deter- 
mine what  degrees  of  contrast  and  dift'erences 
of  gradation  can  be  obtained  with  a  given 
formula. 
2071 


208 


DEVELOPING  SOLUTIONS 


A  sample  formula  may  be  given  as  follows : 

A.  Reducing  agent 2  parts 

Potassium  metabisulphite 1  part 

Water 100  parts 

B.  Anhydrous  sodium  carbonate. .        4  parts 
Water 100  parts 

C.  Ten  per  cent  solution  of  potassium  bromide. 

The  developer  should  be  first  tried  without 
bromide.  Equal  parts  of  A  and  B  will  give 
a  good  but  concentrated  developer. 

The  alkali  is  usually  sodium  carbonate, 
occasionally  potassium  carbonate  and  rarely 
potassium  hydroxide. 

The  preservative  is  sodium  sulphite  which 
prevents  the  rapid  decomposition  of  the  de- 
veloper by  the  air. 

The  restrainer  is  sodium  bromide,  which 
by  supplying  the  bromide  to  the  oxidizer  pre- 
vents the  too  rapid  reduction  of  those  areas 
but  slightly  affected  by  the  light  or  x-rays. 

After  the  individual  chemicals  are  carefully 
weighed  out  on  small  pieces  of  clean  paper, 
they  should  be  individually  dissolved  in  as 
small  amount  of  hot  water  as  possible.  Before 
dissolving  the  Metol  and  Hydrochinon,  a 
small  amount  of  the  sulphite  should  be  mixed 
with  them  loosely  while  dry.  This  will  pre- 
vent oxidation  when  water  is  added.  After 
the  ingredients  are  dissolved  in  a  small 
amount  of  water,  they  are  mixed  together  in 
the   following  manner : 

( 1 )  Pour  together  the  two  developing  so- 

lutions ; 

(2)  Pour  together  the  two  soda  solutions; 
(3),  Add  the   Potassium   Bromide   solution 

to  the  solution  of  sodas ; 
(4)   Add    the    developing    solution    to    the 

solution   of   sodas   and   Bromide. 

This  gives  a  small  amount  of  concentrated 

developer  to  which  the  remaining  amount  of 

cold  water  is  added,  producing  at  the  end  of 

the  operation  a  comparatively  cool  developer. 

IRON  OXALATE  DEVELOPER 
(Keeps  only  in  separate  solutions) 

Solution  A 

Distilled  water 1000  cm. 

Neutral  oxalic  acid  kali 300  g. 

Solution  B 

Distilled  water 300  ccm. 

Sulphate  of  Iron 100  g. 

Acetic  citric  acid 5  g. 

or 
5  drops  of  pure  sulphuric  acid 

or 
Tartaric  acid 7 . 5  gr. 


For  use :  I\Iix  three  parts  of  solution  A  and 
one  part  of  solution  B. 

HYDROQUINONE  DEVELOPER 
Solution  A 

Distilled  water 1000  ccm. 

Sodium  sulphite  crystal -  200  g. . 

Hydroquinone 20  g. 

Solution  B 

Distilled  water 1000  ccm. 

Potassium  carbonate 120  g. 

For  use :  Mix  equal  parts  of  A  and  B.  To 
avoid  fogging,  add  to  every  100  ccm.  of  the 
mixed  developer  five  to  ten  drops  of  a  ten  per 
cent  bromine  solution. 

HYDROQUINONE  DEVELOPER 

Single  solution 

Formula  1 

Water 1000  ccm. 

Sodium  sulphite  crystal 200  g. 

Hydroquinone 50  g. 

Potassium  carbonate  crystal .  .  400  g. 

Potassium  bromide 1 . 5  g. 

For  use :  One  part  of  the  developer  to  four 
parts  of  water. 

Formula  2  (10  minutes) 

Water 1  gallon 

Sodium  sulphite  (dry) 8  ounces 

Hydroquinone 1  1/2  ounces 

Sodium  carbonate 8  ounces 

Potassium  bromide 60  grains 

METOL  DEVELOPER 

Solution  A 

Distilled  water 1000  cm. 

Metol 15  g. 

Sodium  sulphite  crystal 150  g. 

Solution  B 

Distilled  water 1000  cm. 

Potassium  carbonate 30  g. 

Bromide 5g. 

METOL  HYDROQUINONE  DEVELOPER 

Distilled  water 1000  ccm 

Metol 5  g. 

Hydroquinone 8  g. 

Sodium  sulphite  crystal 120  g. 

Potassium  carbonate 150  g. 

Bromide 1 — 2  g. 

or 

Water 20  ounces 

Meto  1 20  grains 

Hydroquinone 80  grains 

Sodium  carbonate  dry 1  ounce 

Sodium  sulphite  dry 1  ounce 

Potassium  bromide 32  grains 


TANK  DE\'ELOPMENT 


209 


The  metol  and  hydroquiiione  must  be  thor- 
oughly dissolved.  The  sulphite  is  added  first 
and  then  the  carbonate.  One  part  solution 
and  two  to  four  parts  water  is  the  ordinary 
mixture  for  developing.  The  development  is 
completed  in  three  to  four  minutes. 

The  development  of  plates,  made  with  the 
intensifying  screens  demands  special  attention, 
because  the  efifect  in  the  plate  is  usually  an 
actinic  one  and  superficial.      (Fig.  224). 

By  the  increase  in  the  amount  of  the  oxidiz- 
ing agent,  less  alkali  and  more  restrainer,  the 
plate  may  be  given  proper  contrast  and  den- 
sity, though  the  time  of  development  will  be 
necessarily  prolonged. 


For  twenty-five  minute  developer:  Solution  A  1000  ccm. 

Solution  B  1000  ccm . 
Water        3000  ccm. 


Glycin 

Sulphite. . . 
Carbonate . 
Water 


2 
5 

10 
100 


For  1/4  to  1/2  hour  developer:  Solution   100  cc. 

Water      1000  cc. 

When  the  plate  is  ready  for  development, 
it  is  removed  from  the  envelope  and  placed 
in  a  special  frame  made  of  metal  and  hung 
vertically  in  a  rubber  or  stone  or  porcelain 
tank,  containing  the  solution  (Fig.  290).  The 
walls  of  the  tank  may  be  grooved  for  the 
reception  of  such  plates  and  the  holders  then 
become  unnecessary. 


METOL  HYDRO  DEVELOPER  FOR  SCREENS 


Metol 

Hydroqu  jnone 

Sodium  carbonate. 
Sodium  sulphite . . . 
Sodium  bromide. . . 
Water 


20  grains 

100  grains 

100  grains 

120  grains 

25  grains 

20  ounces 


Formula  for  Tank  Development 

Tray  development  has  its  advantages  in  that 
it  permits  the  individual  treatment  of  the  plate 
and  the  manipulation  of  the  plate  to  avoid  the 
results  of  over  or  underexposure.  Where, 
however,  the  exposure  is  fairly  correct  and  a 
considerable  number  of  plates  are  to  be  de- 
veloped, tank  development  in  a  diluted  solu- 
tion gives  a  negative,  which  has  average  quali- 
ties. Glycin  is  the  commonly  used  agent  for 
this  purpose. 

Elon-Hydrochinon  Formula 
(Tank) 


Water 

Elon 

Sulphite  of  Soda. 

HvHrnrhinnn 


Avo.rdupois 

6  gallons 

1  oz.,    360  grains 
40  ozs. 

7  ozs.,  145  grains 


ouipiuie  oi  Boaa. ...  4U  oz 

Hydrochinon 7  ozs 

Carbonate  of  Soda. .  40  ozs. 
Potassium  Bromide.  320  grains 

Formula  —  Solution  A 

Glycin 30 

Sulphite 100 

Carbonate 20 

Water 1000 

Solution  B 

Carbonate ICO 

Water 1000 


Metric 
22  liters 
50  grams 

1100  grams 
200  grams 

1100  grams 
20  grams 


The  Fixing  Solution  is  Prepared 
The  Fixing  Solution 

This  consists  of  a  solvent  for  the  unaffected 
bromide  of  silver  emulsion  and  is  almost  uni- 
versally the  hyposulphite  of  soda.  To  pre- 
vent its  rapid  deterioration  and  to  aid  in  the 
hardening  of  the  film  and  in  the  prevention 
of  frilling  or  softening,  other  chemicals  are 
added.  Thus  akmi,  either  in  the  form  of  pow- 
der and  citric  or  acetic  acid  or  the  chrome 
alum  and  sulphuric  acid  are  added  to  the  hypo 
solution. 

Formula  1 

Water 

Hyposulphite  of  soda 

Sodium  sulphite 

Alum  powder 

Citric  acid 


Formula  2 


Water 

Hypo 

Pow.  alum  ... 
Sod.  sulphite  . . 
Acetic  acid  28"^ 


Formula  3 


A.  Water 

Hvpo 

B.  Water 

Chrome  alum . . 
Sulphite  (dry) . 

C.  Water. 


500 

100 

25 

4 

4 

cc. 

g- 

g- 

g- 

g- 

1 
2 

2 

gallon 

pounds 

ounces 

4 

ounces 

6 

ounces 

30 

1 
15 

ounces 
pound 
ounces 

1 

ounce 

2 

ounces 

1/8 

ounces 
ounce 

Sulphuric  acid 

Atid  C  to  B  and  then  mix  with  A.  The 
chemicals  should  be  dissolved  in  the  order 
given. 


210 


DURATION  OF  DEVELOPMENT 


The  Plate  is  Developed 

With  the  ruby  light  dimmed,  the  plate  is 
then  removed  from  the  black  and  red  envel- 
opes and  placed,  sensitive  side  up,  in  a  clean 
tray.  Then  developer,  brought  to  a  tempera- 
ture of  sixty-five  degrees,*  is  poured  from  a 
beaker  on  the  plate,  care  being  taken  to  com- 
pletely cover  the  plate.  The  tray  is  now 
rocked  manually  or  mechanically.  The  rock- 
ing is  necessary  to  keep  the  solution  in  slight 
but  constant  motion  and  prevent  streaking. 
After  a  certain  period,  depending  on  the  devel- 
oper, and  the  intensity  of  the  radiation  to 
which  the  plate  has  been  exposed,  the  image 
begins  to  appear,  due  to  changes  in  those  parts 
of  the  plate  most  affected.  As  development 
proceeds,  the  shadows  of  the  soft  parts  dis- 
appear, and  only  the  outline  of  the  densest 
parts  are  seen.     Development  is  usually  car- 


FiG.  288. — Series  of  vertical  sections  (dry),  showing 
growth  of  image  with  exposure  (sunlight). 
Magniiication,  375  diameters.     (Hodson.) 

ried  on  until  these  fade  out.  The  determina- 
tion of  the  duration  of  development  may  be 
made  in  three  ways  : 

*  For  each  5"   increase  in  temperature  the  devel- 
oping time  should  be  decreased  3$%. 


1.  By    examination    by    transmitted    light. 
The  negative  appears  denser  by  the  ruby  light. 

2.  Examination    by    reflected    light  «jDf    the 
back  of  the  plate. 

3.  The  factorial  system. 


>  ^?fr:'v^:=V^v^^> 


Fic.  289. — Series 
development. 
( Hodgson.) 


showhig    growth    of    image    with 
Magnification,      375      diameters. 


1.  Viewed  by  transmitted  light,  the  fully 
developed  negative  barely  transmits  the  light. 
It  loses  some  of  this  density  in  the  fixing  bath. 

2.  Viewed  by  reflected  light,  the  image 
should  be  clearly  visible  on  the  reverse  side. 
This  is  usually  attained  by  a  7  minute  de- 
veloper at  65°  with  a  Seed  plate. 

3.  By  this  method  the  duration  of  develop- 
ment is  determined  by  noting  the  time  of  ap- 
pearance of  the  first  trace  of  the  image  on  the 
plate  and  multiplying  this  time  by  a  factor — 


FIXING  AND  DRYING 


211 


the  result  being  the  total  duration  of  develop- 
ment necessary  to  produce  a  plate  of  certain 
density. 

Each  developing  agent  in  normal  solu- 
tion has  a  certain  factorial  developing  time. 
Thus  the  factor  of  a  particular  developer  may 


Thtse  Cemparfmenfs 
15/nches  lontj  inside 


T/iese  ^ompsrhtmk 
"     IStnches  toni 


-* —  40^  inches ^ 

Fig.  290. — Tank  developing  system. 

be  sixteen.  If  the  image  appears  in  fifteen 
seconds  and  the  factor  of  the  particular  de- 
veloper is  sixteen,  the  plate  will  be  fully  de- 
veloped in  four  minutes.  The  factor  of  metol 
hydroquinone  developer  is  14. 

When  the  development  is  complete,  the  plate 
is  washed  in  water  to  remove  the  superfluous 
developer,  for  the  alkali  prevents  the  action 
of  the  hypo  bath  and  at  the  same  time  dis- 
colors it.  The  hypo  solution  must  be  kept  out 
of  the  developing  solution. 

Fixing  should  be  done  in  yellow  but  not  in 
white  light,  because  fogging  will  take  place. 
\Mien  the  unafifected  silver  has  been  thoroughly 
cleaned  ofif  the  plate  and  the  emulsion  is  prop- 
erly hardened,  the  plate  is  ready  for  its  final 
washing  to  remove  the  chemicals. 

The  hypo  may  be  rapidly  eliminated  by  a 
solution  of  peroxide  of  hydrogen. 

If  special  water  tanks  are  used,  the  plate  is 
placed  therein  and  allowed  to  wash  for  about 
an  hour.  Before  removing  from  the  washing 
tank,  the  surface  of  the  plate  should  be  washed 
with  a  soft  sponge  or  cotton  to  remove  the 
dirt  sediment  of  the  water. 

Drying 

The  plate  should  not  be  placed  to  dry  in 
the  direct  sunlight  or  under  an  open  flame, 
because  the  gelatine  would  melt.     A  current 


of  air  is  valuable  for  rapid  drying.  The  plate 
should  not  be  moved  about  the  room.  A  plate 
may  be  rapidly  dried  in  alcohol  by  first  re- 
moving the  superfluous  water,  then  placing  it 
in  concentrated  alcohol  for  five  or  ten  minutes. 
The  alcohol  withdraws  the  water  from  the 
plate.  There  is  usually  an  increase  in  density 
in  this  method  of  fixation. 

Rapid  drying  may  also  be  accomplished  by 
the  use  of  certain  salts  in  concentrated  solu- 
tion. This  is  only  a  temporary  method.  Thus 
sulphite  of  alumina  100%  solution  produces 
complete  dehydration.  Among  other  salts 
doing  this  are  ammonia  sulphate  (75%  solu- 
tion) sulphate  soda  (anhydrous  50%  solu- 
tion) sulphate  of  zinc  (160%  solution). 
According  to  Lumiere  and  Seyewetz,  carbon- 
ate of  potash  in  saturated  (cold)  solution  (90 
grammes  in  100  c.  c.  of  water)  dries  nega- 
tives rapidly  and  yet  causes  no  altera- 
tion of  the  gelatine,  even  after  prolonged 
contact.  The  negative  is  plunged  into  this 
saturative  solution  and  washed  for  a  minute. 
The  surface  water  is  then  removed.  It  is 
then  immersed  again  for  four  or  five  min- 
utes   in   the    saturated    aqueous     solution     of 


Fig.  291.— Method  of  drying  dental  films. 

potassium  carbonate  and  pressed  between  blot- 
ting paper  to  remove  the  greater  part  of  the 
alkaline  solution.  Drying  is  completed  by 
wiping  the  gelatine  coating  with  a  linen  cloth. 
The  plate  may  later  be  washed  and  dried  in 
the   regular   way. 


212 


INTENSIFICATION 


Intensifying 

Previous  to  intensification,  the  plate  must 
be  thoroughly  fixed  and  washed  if  streaking 
is  to  be  avoided.  Better  intensification  is 
obtained  if  the  plate  has  been  well  dried,  and 
soaked  just  previous  to  the  intensification. 

Solution  1 

Bromide  Potass 50  g. 

Mercury  bichloride 50  g. 

Water 1000  ccm. 

Solution  2 

Liq.  ammon.  caust 100  cm. 

Water 1000  ccm. 

These  solutions  keep  and  may  be  used  re- 
peatedly. 

The  plate  to  be  intensified  is  soaked  and 
then  placed  in  Solution  1  and  constantly 
rocked  until  it  becomes  gray.  The  negative 
is  washed  for  about  fifteen  minutes  and  then 
put  in  solution  2  and  rocked.  As  soon  as  the 
negative  has  assumed  an  even,  dark  tone,  it 
is  removed  and  washed  for  about  an  hour 
and  dried. 


URANIUM  INTENSIFIER 
Solution  1 

Uranium  nitricum 1  g 

Distilled  water 100  ccm. 

Solution  2 

Kal.  ferricyanide  rubr 1  g. 

Distilled  water 100  ccm. 

Solution  3 
Acid  acetic  glac. 
For  use  mix  in  following  manner : 

Solution  1 50  ccm. 

Glacial  acetic  acid 10  ccm. 

Solution  2 50  ccm. 

The  plate  to   be   intensified  is  kept  in  the 

solution  until  it  is  dark  reddish.     It  is  then 

washed. 

Reducing 

Solution  1 

Distilled  water 1000  ccm. 

Sod.  hyposulphite 100  g. 

Solution  2 

Distilled  water 100  ccm. 

Potas  ferricyanide 20  g. 

(Red  Prussiate) 

For  use 

Solution  1 100  ccm. 

Solution  2 5  ccm. 

The   negative   must  be   thoroughly  washed 

to  remove  the  hypo. 


CHAPTER  XXI 

THE  EXAMINATION  OF  THE  PLATE 

The  Plate  is  Recorded 

As  the  plate  comes  from  the  dark  room,  it 
has  on  it  the  radiograph  of  the  lead  number 
which  has  been  placed  on  it  before  exposure. 
The  plate  should  now  be  labelled.  The  label 
should  bear  the  name  of  the  patient,  the  date 
of  the  examination,  the  place  of  examination, 
a  number  corresponding  to  that  on  the  plate, 
and  such  other  data  as  may  be  desired.  The 
label  should  be  placed  on  the  glass  side. 
Screen  plates  may  be  marked  by  writing 
the  data  on  a  piece  of  thin  paper  and  placing 


Fig.  2g2. —  Plate  illuminating  box  for  use  with  re- 
flected light.  The  nitrogen  bulbs  are  completely 
hidden  from  the  eye. 

this  between  plate  and  screen.     The  exposure 
transfers  this  data  to  the  plate. 

The  Plate  is  Examined 

The  illumination  for  this  purpose  may  be 
of  three  varieties. 

1.  Daylight. 

2.  Transmitted  light  (Cooper  Hewitt  light). 

3.  Reflected  light  (incandescent  or  tung- 
sten). 

The  north  light,  particularly  as  transmitted 
through  a  thin  ground  glass  gives  excellent 
illumination  of  the  plate.  The  uncertainty  of 
unobstructed  daylight  in  large  cities  renders 
this  method  generally  unavailable. 


Transmitted  Light 

Such  illuminating  devices  consist  of  wooden 
or   metal   boxes    in   which    several   lights   are 

-II  — 


emd    ell-evatiom 
Simqle:    wiisdow    feame 

OUTFIT. 

Fig.  293 


EIND      ELEVATIOM 

OOU&LE     WIHDOW      FieAME 
OUTFIT. 

Fig.  294 


[213] 


214 


EXAMINATION  BY  REFLECTED  LIGHT 


placed  behind  a  window  of  ground  glass.  The 
light  is  first  generally  diffused  by  the  use  of 
tracing  cloth  or  paper.  It  should  be  consid- 
ered an  essential  in  such  construction  that  the 
plate  to  be  viewed  rest  not  against  the  ground 
glass  but  at  a  distance  of  two  inches  from  it, 
preferably  against  a  sheet  of  clear  glass. 
Instead  of  ground  glass,  the  so-called 
"  blazed  glass  "  may  be  used  as  a  diffusing 
media.  This  needs  no  paper  diffusion  and  is 
very  serviceable.  Instead  of  tungsten  lamps, 
blue  glass  nitrogen  lamps  are  of  late  utilized 
and  give  powerful  illumination  but  generate 
considerable  heat.  The  box  should  be  painted 
white  within  and  the  lights  be  so  disposed  as 
to  aid  diffusion.  The  front  of  the  box  should 
be  provided  with  a  double  black  curtain  ar- 
rangement for  the  accommodation  of  plates  of 
all  sizes.  Means  for  dimming  the  illumination 
should  also  be  provided.  These  boxes  may 
be  constructed  with  an  illuminating  surface 
measuring  17  x  17  inches,  this  accommodating 


unnecessary,  if  a  sufficient  ledge  is  provided 
below  to  hold  the  bottom  plate.  Thejedge 
should  be  of  metal  and  abut  directly  against 
the  glass. 

-64- 


rRO'~tT       El_EVATIOr-(. 

Fig.  295 

Figs.   293,   294,   295,   296. — Plate    illuminating  boxes 

fitted  with  Cooper-Hewitt  lamps. 

Reflected  Light 

In  this  form  of  illumination  the  lights  are 
shaded  and  reflected  from  a  white  background 


2  WIRE    •  14  RtlNFWCED  CflBLt 


ei-T^aiX     TOP  I/,"C0NDU.T  \ 


CONUULtT   SwnCK    I 


APPROVED      PLuq 

TOP  VIEW 

Fig.  296. — Revolvable  illuminating  box. 


tut  one  14  x  17  plate,  or  the  illuminated  sur- 
face ma}-  be  much  larger.  In  the  latter 
variety,  the  illuminated  window  must  be  in- 
clined to  such  an  extent  as  to  permit  the  plac- 
ing of  several  plates  upon  each  other  on 
edge.      Framework   to   hold   these   plates   are 


through  a  clear  glass  window  against  which 
the  plates  are  placed.  (Fig.  292.)  This  is 
undoubtedly  the  best  form  of  illumination  but 
requires  greater  strength.  The  construction 
of  the  box  should  be  such  that  the  reflecting 
back  is  not  too  far  behind  the  glass  and  the 


COOPER— HEWITT  LAMPS 


215 


source    of    illumination    must    be    completely      mitted.  incandescent  or  mercury  vapor  illumi- 

hidden  from  the  eye.  nation.     This   box   occupies   but    small   space 

As    a    source    of    illumination    the    Cooper 


3     Z 


Fig,  297. — Case  for  filing  and  examining  reductions 
(lantern  slides).  The  frame  is  usually  drawn 
out  in  front  of  an  illuminated  surface.  Fig.  299. — The  Wheatstone  or  reflecting  stereoscope. 


Hewitt  mercury  vapor  tubes  is  to  be  preferred 
to  any  other  and  may  be  applied  in  boxes  con- 
structed either  for  transmitted  or  reflected  light. 
(Figs.  293,  294,  296).  If  not  too  bright  and 
properly  diffused,  it  is  by  far  the  best  source 


and  permits  the  inspection  of  six  plates  of  the 
largest  size.      (Fig.  296.) 

Viewing  of  Stereo  Plates 

Stereoscopic  exposures   may  be  viewed   in 
several  ways : 

1.  Prism  stereoscopes. 


Fig.  298. — The  refracting  or  prism   stereoscope. 


Fig.  300. — The   single   mirror   reflecting  stereoscope. 


2.  W'heatstone  stereoscopes. 

3.  Mirror   stereoscope   of    Hegener. 


of    illumination.     For    its    equivalent    candle 

power    it    is    cheaper    than    the    incandescent      '  '  '^"'  ^  'creoscopc 

light.     It  generates  but  little  heat.     A  revolv 

able  box  mav  be  arranged  both  for  the  trans 


These  are  most  commonly  used  with  reduc- 
tions from  the  large  plates  but  the  disadvan- 


216 


VIEWING  OF  STEREOSCOPIC  PLATES 


tage  here  is  the  delay  which  results  before  the 
plates  can  be  examined.  Prism  stereoscopes 
have,  however,  been  constructed  with  which 
the  full  sized  plate  may  be  examined.  These 
are  placed  on  a  flat  illuminated  surface  and 
viewed  through  the  prisms.  The  objection  to 
their  use  lies  in  the  necessity  of  viewing  the 
plates  from  a  great  distance.      (Fig.  298.) 

Whcatstonc  Stereoscope 

This  is  the  most  commonly  used  method. 
The  plates  are  placed  in  illuminating  boxes  to 
either  side  of  a  Wheatstone  mirror.  The  plate 
with  the  foot  point  to  the  right  is  placed  to 
the  right  of  the  observer,  and  the  one  with 
the  left  to  the  left.  The  eyes  are  now  ap- 
plied to  the  mirror,  the  right  eye  looking  into 
the  right  mirror  and  the  left  into  the  left.  The 
mirrors  are  pushed  forward  or  back  until  both 
the  images  coincide.  A  four-sided  viewing 
box  in  which,  by  revolving  the  boxes,  the  dif- 
ferent sets  may  be  brought  to  view  is  a  con- 
venience.     (Fig.  299.) 


Mirror  Stereoscope 

This  method  has  the  advantage  in  that  it 
needs  no  special  apparatus  or  viewing  arrange- 
ment. The  plates  are  placed  on  the  usually 
illuminated  surface,  one  with  sensitive  side 
to  observer  and  one  with  glass  side.  The  mir- 
ror is  then  held  between  the  eyes.  One  eye 
views  the  plate  directly.  The  other  eye  views 
the  other  plate  in  the  mirror  and  the  stereo- 
scopic effect  is  obtained  by  varying  the  dis- 
tance of  the  eye  from  the  plates.      (  Fig.  300.) 

Sytnphany 

Eykman  has  modified  the  viewing  of  the 
stereoscopic  image  by  using  transparent,  in- 
stead of  opaque  mirrors.  By  this  means  the 
Roentgen  picture  is  seen  as  a  phantom  image, 
which  appears  solid  and  in  which  a  ruler  may 
be  inserted  and  the  exact  distance  between 
any  two  points  measured.  By  this  method 
the  radiograph  may  be  viewed  simultaneously 
with  an  ordinary  stereoscopic  photograph  of 
the  object  reduced  to  the  same  size. 


] ■ ~    • r 

n" 

GROUND     GLASS 
8-8" 

\ 

n 

y 

^ 

II 

1! 

' 

" 

11                                       !1 

i1 

Fig.  301. — Plate-illuminatinj 


ELEVATION 

box  with  filing  cabinet. 


SECTION 

Either    transmitted    or    reflected    light    may    be  used. 


CHAPTER  XXII 
THE  X-RAY  LABORATORY 

The  api)lication  of  the  Roentgen  Rays  as  a 
diagnostic  agent  in  every  field  of  medicine  and 
surgery  has  made  the  x-ray  department  in- 
dispensable in  a  hospital  organization. 

Though  it  is  acknowledged  that  the  art  of 
Roentgen  diagnosis  has  not  yet  reached  its 
highest  and  fullest  development,  it  cannot,  on 
the  other  hand,  be  denied  that  it  has  made 
tremendous  strides  and  conquered  many  fields, 
helping  and  benefiting  the  surgeon  and  phy- 
sician in  innumerable  ways. 

It  might  seem  that  at  this  late  day,  it  would 
be  unnecessary  to  argue  for  the  value  of  the 
Roentgen  Ray  laboratory  as  a  diagnostic 
agency,  but  the  state  of  this  department  in 
many  hospitals  seems  to  indicate  a  rather  tardy 
recognition  of  the  service  it  can  render  in 
medicine  and  surgery,  and  the  responsibility 
for  this  cannot  be  placed  entirely  on  the  man- 
agement or  the  lay  officers. 

The  object  should  be  to  organize  a  useful 
and  active  department,  which  should  be  made 
to  play  an  important  role  in  the  clinical  activi- 
ties of  the  hospital. 

A  well  organized  and  equipped  x-ray  labora- 
tory becomes  the  repository  of  a  vast  amount 
of  interesting  material,  to  the  study  of  which 
it  is  asked  to  give  its  contribution.  It  be- 
comes, so  to  speak,  the  clearing  house  for 
the  undiagnosed,  difficult  and  interesting  cases 
in  the  hospital,  and  rationally  applied,  it  bene- 
fits the  hospital  generally  by  permitting  an 
early  diagnosis,  indicating  a  more  rational 
therapy  and  resulting  in  the  end  in  shortening 
the  stay  of  the  patient  in  the  hospital. 

The  Roentgen  laboratorj'  is  essentially  a 
clinical  laboratory,  because  it  deals  with 
patients,  and  it  is,  therefore,  necessary  that 
such  a  laboratory  should  be  a  distinct  adjunct 
and  closely  associated  with  the  hospital  wards. 

Organisation 

In  the  organization  of  a  department,  it 
should   be   borne   in   mind   that   its    important 


function  is  the  diagnosis  or  the  reading  of 
the  plate — in  other  words — that  the  object  for 
which  the  laboratory  exists  is  to  report  the 
results  of  the  examination  and  that  the  mak- 
ing of  the  plate  is  only  the  means  to  an  end, 
and  that  it  is  more  important  to  make  the 
plate  radiographically  useful  than  photograph- 
ically perfect,  and  that  these  are  not  always 
synonymous. 

What  should  be  required  of  a  department 
is : 

1.  That  the  results  of  the  examination 
should  in  a  usual  case  be  available  within 
twenty-four  hours. 

2.  That  a  complete  record,  consisting  of 
report  of  the  finding  and  a  diagram  or  print 
of  the  plate,  should  be  appended  to  the  his- 
tory. 

3.  That  the  plates  should  be  so  filed  as  to- 
be  quickly  isolated,  and  so  classified  as  to  be 
readily  available  for  systematic  study. 

These  problems  should  be  solved  in  an 
economical  manner  as  regards  labor,  time  and 
money. 

In  the  organization  of  a  department,  it  is 
important  to  consider : 

1.  The  size  of  the  service. 

2.  The  variety  of  the  service. 

3.  ^Money  available  for  equipment  and 
maintenance. 

The  organization  of  a  department  of  a  hos- 
pital of  one  hundred  beds  would  differ  in 
many  respects  from  that  of  a  hospital  of  1,000 
beds.  So,  also,  a  laboratory  for  the  complete 
service  of  eye,  ear,  nose  and  throat  would  in 
many  respects  be  dift'erently  assembled  from 
a  laboratory  for  medical  and  surgical  service. 

In  a  general  way,  it  may  be  stated  that  the 
average  hospital,  doing  roentgenographic  work 
according  to  modern  standards,  will  examine 
during  the  vear  a  number  of  patients  equal 
to  si.x  times  the  number  of  beds.  Thus  a  hos- 
pital of  120  beds  will  normally  examine  about 
800  patients  a  year,  of  which  about  2,000 
plates  will  be  made.  A  hospital  of  300  beds 
12171 


218 


EQUIPMENT 


will  examine  2,000  patients  a  year,  of  which 
about  5,000  plates  will  be  made,  etc.,  while 
about  8.000  patients  should  normally  be  exam- 
ined with  20,000  plates  in  a  hospital  of  1,300 
beds.  It  is  impossible  to  establish  any  definite 
ratio  of  plate  to  patient.  The  above  figures 
are  but  loose  averages.  Generally  speaking, 
therefore,  laboratories  may  be  divided  into 
three  classes — small,  medium  and  large. 

Equipment  and  Maintenance 

The  equipment  and  maintenance  of  an 
efficient  roentgen  department  is  an  expensive 
item  in  hospital  economies,  and  there  is  ap- 
parently no  limit  to  the  expenditure  which 
may  be  made  for  apparatus  and  equipment. 
The  apparatus,  appliances  and  even  the  actual 
maintenance  are  far  more  costly  than  for  a 
pathological  laborator}'. 

The  contention  that  it  is  possible  to  main- 
tain an  efficient  department  according  to  mod- 
ern standards  at  a  moderate  cost  cannot  be 
disputed.  There  are  certain  absolute  essen- 
tials, without  which  no  department  can  do 
efficient  work,  and  it  is  an  investment  making 
for  eventual  economy  to  obtain  the  most 
efficient,  essential  apparatus  at  the  beginning. 
In  addition  to  these,  there  are  a  multitude 
of  accessory  appliances  which  are  to  be  con- 
sidered luxuries ;  yet,  the  question  of  just  how 
much  equipment  a  hospital  is  to  purchase  is 
a  difficult  one  to  decide,  because  of  the  over- 
enthusiasm  of  the  mechanically  untried  worker 
on  the  one  hand,  allured  by  new  and  glitter- 
ing devices,  and  the  uninterested,  uninstructed 
lay  official  on  the  other,  with  the  result  that 
there  may  be  an  appalling  wastefulness  in 
the  management  of  the  laboratories,  useful 
apparatus  being  frequently  discarded  for  new- 
fangled ideas. 

Certain  limitations  in  the  expenditure  will 
be  met  with  in  every  institution,  and  it  is  not 
to  be  forgotten  that  doing  the  necessary  work 
efficiently,  in  spite  of  certain  limitations  shows 
the  master. 

It  is  the  undoubted  aim  of  every  institution 
that  its  department  shall  be  self-maintaining. 
This  is  indeed  possible  in  institutions  having 


large  private  pavilions  where  a  fee  for  such 
extra  examinations  can  be  made.  There  are, 
however,  relatively  few  institutions  where  it 
is  possible  to  obtain  sufficient  income  from 
this  source  with  the  result  that  the  hospitals 
encourage  their  stafl^s  to  refer  to  the  depart- 
ment outside  patients  from  their  own  private 
practice. 

The  question  then  arises,  has  the  hospital 
a  right  to  engage  in  private  practice,  or 
should  its  activities  be  confined  to  patients 
treated  in  its  wards  or  dispensaries  ?  As  an 
isolated,  bold  proposition  this  admits  of  but 
little  argument.  For  it  is  generally  acknowl- 
edged that  an  endowed  institution  is  not 
privileged  to  engage  in  private  practice.  On 
the  other  hand,  if  the  roentgenologist  benefits 
by  this  arrangement  in  much  the  same  way  as 
the  attending  surgeon  or  physician  does  by  the 
admission  to  the  hospital  of  patients  into  his 
service,  then  it  cannot  be  denied  that  it  is  its 
right  to  accept  such  work.  However,  this  has 
been  corrupted  into  a  practice  by  which  the 
hospital  employs  its  roentgenologist  at  a  fixed 
salary,  advertises  its  facilities,  reaps  the  bene- 
fits of  his  labors  and  credits  to  itself  any  sur- 
plus. This  is  obviously  unfair,  and  is  but 
one  of  many  problems  of  this  kind  which  must 
be  solved  by  co-operation  between  the  roent- 
genologist and  the  institution. 

To  have  a  laboratory  of  the  highest  effi- 
ciency and  greatest  utility  there  is  necessary 
in  its  organization : 

1.  Efficient  direction. 

2.  Efficient  assistance. 

3.  Sufficient  apparatus  and  equipment. 

4.  Sufficient  room. 

Management 

To  buy  costly  apparatus  and  permit  the 
work  to  be  performed  by  the  untrained  and 
under  the  haphazard  direction  of  a  medical 
staff,  leads  to  eventual  dissatisfaction  and  dis- 
credit. To  equip  a  laboratory  and  then  fail 
to  provide  it  with  a  competent  director,  par- 
ticularly interested  in  the  work,  is  a  futile 
proceeding. 

In  a  small  laboratory  with  a  normal  service 


MANAGEMENT 


219 


of  600  to  800  patients  or  less,  it  is  possible  for 
the  entire  work  to  be  done  by  one  individual ; 
but  under  these  circumstances  a  daily  attend- 
ance in  the  laboratory  for  at  least  five  hours 
is  necessary. 

In  larger  laboratories  this  becomes  almost 
impossible  and  an  increase  in  the  working 
staff  becomes  imperative,  the  increase  being 
in  proportion  to  the  size  and  variety  of  service. 

The  director  of  the  laboratory  should  in  all 
cases  be  a  medical  man,  who  has  devoted  him- 
self to  roentgenology  as  a  specialty.  It  is 
difficult  to  mention  a  specialty  which  requires 
so  considerable  and  varied  an  experience  and 
knowledge,  so  thorough  a  fundamental  edu- 
cation, and  so  comprehensive  a  view  of  medi- 
cine and  surgery  as  does  this  art  of  clinical 
diagnosis. 

The  working  staff'  may  be  increased  by  the 
addition  of  the  following: 

1.  Photographic  assistant  to  assume  charge 
of  all  the  dark  room  activities. 

2.  Nurse  to  assist  in  the  preparation  of 
the  patient  for  examination,  and  to  act  as 
executive  secretary,  assuming  charge  of  the 
records,  filing,  indexing,  etc. 

3.  Technician  to  make  the  plate  examina- 
tion and  keep  the  apparatus  in  order. 

4.  A  stenographer  for  the  purpose  of  re- 
ceiving dictation  on  the  reports  of  the  exam- 
ination and  doing  clerical  work. 

For  small  laboratories  a  nurse  may  be 
trained  to  perform  the  duties  of  the  photo- 
grapher, technician  and  executive  secretary, 
and  in  the  majority  of  smaller  laboratories, 
this  is  done ;  but  in  the  large  laboratories  a 
further  division  of  labor  becomes  necessary, 
and  this  should  be  in  the  direction,  first,  of 
obtaining  a  dark-room  assistant,  and  secondly 
in  the  enlistment  of  the  services  of  a  stenog- 
rapher. 

The  result  of  the  first  addition  is  to  limit 
the  activities  of  the  director  to  the  actual  mak- 
ing of  examinations,  both  fluoroscopic  and 
plate,  thus  permitting  him  to  give  more  time 
to  work  that  is  more  properly  within  his 
sphere.  The  result  of  the  second  addition  is 
to  increase  the  value  of  the  examinations  bv 


making  for  full,  complete,  and  detailed  reports, 
for  accurate  filing  and  cross-indexing,  etc. 
Without  this  assistance,  in  busy  laboratories, 
the  reports  may  degenerate  into  the  making  of 
mere  diagnostic  labels,  which  are  frequently 
valueless  and  uninstructive,  while  the  material 
itself   becomes   useless   and   a   burden. 

Director 

The  detailed  duties  of  the  director  are: 

1.  General  control. 

2.  Special  work. 
__(a)   Fluoroscopy. 

(b)  Radiography.  Though  it  is  not  essen- 
tial that  he  make  all  the  radiographic  exam- 
inations (plates)  himself,  it  is  important  that 
he  direct  the  activities  of  the  technician  in  each 
particular  case.  Thus,  before  the  examination 
is  made,  he  should  place  brief  instructions  on 
the  requisition  card. 

(c)  Reading  and  reporting  the  plates. 
There  has  been  considerable  difference  of 

opinion  regarding  the  nature  of  the  reports 
submitted  by  the  roentgenologist.  It  has  been 
claimed  by  some  that  a  report  of  findings  in 
reference  to  shadows,  etc.,  is  sufficient,  the 
interpretation  thereof  to  be  left  to  the  clin- 
ician. It  is  this  attempt  to  make  the  roentgen 
laboratory  a  mere  picture  shop  which  retards 
the  advancement  of  the  art.  The  sole  object 
of  the  existence  of  the  laboratory  is  to  pro- 
duce results.  The  plate  examination  is  but  the 
means  to  an  end — its  interpretation.  It  is  just 
as  illogical  as  to  request  the  pathologist  that  he 
confine  his  activities  to  the  cutting,  staining 
and  mounting  of  the  specimen,  and  leave  the 
diagnosis  to  the  clinician. 

The  report  should  consist  of : 

1.  Description  of  the  plate  shadows, 

2.  Interpretation  in  the  light  of  recognized 
accepted  findings. 

If  possible  cooperative  methods  should  be 
introduced  into  the  departments.  The  sur- 
geon and  staff  should  at  a  certain  hour  daily 
visit  the  department,  bringing  with  them  the 
clinical  history  of  the  cases.  These  are  read  and 
discussed  in  the  lisrht  of  x-rav  findings,  and  the 


220 


ROUTINE 


necessary   additional   examinations    are   made 
and  conclusions  reached. 

Since  roentgenology  is  not  a  finished  art,  it 
is  only  by  clinical  and  pathological  correction 
and  elucidation  that  definitenes-s  and  accuracy 
can  be  reached  and  the  true  value  of  the  ex- 
amination established.  Only  by  the  combined 
effort  of  the  medical  staff"  and  the  roentgen- 
ray  laboratory  will  anything  permanent  in  this 
direction  be  accomplished. 


well  be  applied  to  any  service  or  any  labora- 
tory. 

Requisition   cards    for   x-ray   examinations 
(Fig.  302),  bearing  the  signature  of  the  at- 
tending physician  or  surgeon  and  the  superin-  - 
tendent  of  the  hospital,  are  submitted  to  the 
department   in  the   morning,   if   examinations , 
are  to  be  made  on  that  day.     This  refers  to  a 
busy  laboratory  only,  where  it  becomes  neces- . 
sary  to  plan  the  work,  and  where  the  actual 


B  ELLEVUE  HOSPITAL  —  DEPARTMENT  OF  RADIOLOGY 


Name 

Age Ward O.  P.  D.. 

Resident  Physician 

Attending 

Superintendent 

Date 


Clinical  Diagnosis.. 


Part.. 


Plate  No 

Part,  position 

Tube 

Exposure,  Milliamp.,  Gap.. 


X-Rav  diagnosis,. 


Fig  302.     Requisition  card  for  X-Ray  examination  —  Size  4x6  inches. 

Data  above  first  black  line  is  filled  in  by  the  medical  staff.    Data  between  the  first  and  second  black  lines  is 
filled  in  while  the  examination  is  made.     The  X-Ray  diagnosis  is  filled  in  after  the  plate  has  been  read. 


Routine 

It  is  clearly  appreciated  that  no  one  system 
or  method  can  be  outlined  to  cover  every  con- 
dition and  environment.  Though  certain  defi- 
nite standards  have  already  been  generally 
adopted,  it  nevertheless  must  be  borne  in  mind 
that  there  are  still  many  mooted  questions  and 
changing  conditions  requiring  constant  realign- 
ment. The  test  of  any  particular  organization 
or  routine  should  be  that  it  is  practical,  flexible 
and  that  it  meets  in  a  satisfactory  manner  the 
requirements  of  large,  active  and  exacting 
services. 

The  routine,  with  few  modifications,  might 


plate  examination  work  must  be  finished  at 
a  certain  hour.  The  signature  of  the  attend- 
ing physician  is  necessary  in  order  to  hold 
in  check  the  enthusiasm  of  an  interested  house 
staff'  for  the  roentgen  demonstration  of  con- 
ditions where  no  difficult  problem  exists  in 
diagnosis.  The  signature  of  the  superinten- 
dent is  important  in  order  that  he  may  thus 
keep  in  touch  with  the  amount  of  work  the 
department  is  doing. 

The  patient  may  be  brought  to  the  depart- 
ment by  a  nurse  or  orderly  from  a  ward,  or 
by  a  special  orderly  attached  to  the  x-ray  de- 
partment.    The  latter  method  is  the  best  in 


REPORTS 


221 


large  hospitals,  for  considerable  time  is  saved 
by  the  nurses  of  the  wards  and  it  becomes  also 
unnecessary  for  them  to  wait  in  the  depart- 
ment until  the  examination  is  finished.  Ex- 
aminations are  made,  if  possible,  during  the 
morning  hours,  the  afternoon  being  devoted 
to  fluoroscopy,  and  to  developing,  recording 
and  study  of  plates. 

A  report  of  the  radiographic  findings  should 
be  dictated  to  the  stenographer  the  following 
day.  The  plates,  labeled,  should  then  be 
placed  on  illuminating  boxes  for  the  purpose 
of  observation  by  the  stai¥. 


in  large  filing  cabinets  by  the  aid  of  filing 
guides,  and  this  is  done  either  daily  or  weekly. 
When  done  weekly,  the  daily  plates  are  placed 
according  to  the  name  of  the  patient  into  let- 
tered compartments  placed  under  the  illumin- 
ating boxes. 

For  the  rapid  isolation  of  a  plate,  a  day 
book  is  kept,  wherein  is  recorded  the  data  of 
the  requisition  card ;  the  x-ray  diagnosis,  etc., 
being  entered  the  following  day.  A  daily  re- 
port card  (Fig.  304)  is  sent  to  the  superintend- 
ent, giving  the  number  of  patients  from  each 
service,  the  number  of  free  and  the  number 


BELLEVUE  HOSPITAL  —  DEPARTMENT  OF  RADIOLOGY 


Disease 


Name 


Plate  No. 


Remarks 


Fig.  303.     Diagnosis  card  —  Size,  4x6  inches 


Three  copies  of  each  report  are  made,  one 
being  filed  in  the  department,  under  the  name 
of  patient,  one  classified  in  a  disease  index 
and  sent  to  the  ward  to  be  filed  with 
the  ward  histories.  These  duplicate  reports 
filed  in  the  department  may  be  appended 
to  the  plates  as  they  are  laid  out  for  in- 
spection and  thus  save  the  director  the  neces- 
sity of  personally  explaining  each  plate  to 
those  calling  at  the  department.  In  addition 
to  this,  prints  which  best  illustrate  the  results 
of  the  examinations  are  filed  with  the  history 
chart,  either  in  all  cases  or  where  requested. 
The  original  requisition  cards  are  filed  in 
alphabetical  order  according  to  the  name  of 
the  patient.  A  diagnostic  card  system  should 
also  be  kept  which  classifies  the  radiographs 
according  to  the  pathological  conditions  (Fig. 
303).    The  plates  are  filed  in  numerical  order 


of  pay  patients,  etc.  This  is  returned  to  the 
department  and  filed  under  the  date,  and  is 
useful  at  the  end  of  the  year  in  the  produc- 
tion of  the   annual   report. 

When  plates  are  taken  from  the  depart- 
ment, they  are  signed  for.  When  given  to 
the  dark  room  for  printing  or  reducing,  etc., 
the  plate  is  replaced  in  the  file  by  a  red  card. 
By  this  method  it  is  possible  to  determine 
where  any  particular  plate  is,  and  to  locate  it 
when  inspection  is  desired. 

The  routine  carries  out  the  objects  and  pur- 
poses of  an  x-ray  laboratory,  and  it  is  only 
by  following  this  or  a  similar  routine  that 
any  method  or  system  can  be  maintained. 
For,  in  a  well-organized  laboratory  each 
worker,  from  the  medical  director  to  the 
orderly,  has  particular  tasks  and  duties,  and 


222 


PLANNING  OF  LABORATORY 


there   is   a  particular   time   in   which   this   or 
that  task  is  to  be  performed. 

It  will  be  at  once  apparent  that  since  there 
are  numerous  and  varied  tasks  and  duties  to 
be  performed,  a  certain  amount  of  division 
of  labor  becomes  necessary  as  the  laboratory 
attains  anv  considerable  size. 


In  some  large  hospitals  there  are  frequently 
two  distinct  departments,  one  for  the  outdoor 
and  one  for  the  hospital  patients.  In«iact,  the 
particular  medical  and  surgical  services  each 
have  for  themselves  a  special  department. 
This,  however,  does  not  commonly  obtain  and 
perhaps   it   is   better   so.       Centralization,   on 


BELLEVUE  HOSPITAL  —  DEPARTMENT  OF  RADIOLOGY 


Date.. 


Division 

Child 

S 

M 

Gyn. 

G.U. 

Clinic 

0.  P. 

Pay 

Free 

Amt. 

Series 

No.  Total 

No.  of  patient 

s 

Tubes 

Exp's 

Diseases 

No. 

Notes 

1 

Circulat.  sy 
Respir.  syst 
Gastro.  int. 
Urinary  sys 
Pregnanrv 

St 

1 

syst 

t 

Join 
Bon 
Frac 
Disl 

ts 

es             

tures 

oration 

s                .          

Foreign  Bo 
Misrellaner 

Fig.  304.  Daily  record  card.- 
made  with  each  tube. 

Accommodations 

The  space  devoted  to  the  x-ray  department 
should  be  ample.  In  most  laboratories  the 
space  is  entirely  inadequate.  The  tendency 
exists  to  put  the  x-ray  department  in  the  most 
out-of-the-way,  inaccessible  and  unsanitary 
part  of  the  building.  In  the  location  of  the 
x-ray  department  there  are  two  points  to  be 
considered : 

1.  The  outdoor  patients. 

2.  The  hospital  patients. 


-  Size,  4x6  inches,  gives  summary  of  day's  work,  including  number  of  exposures 


the  whole,  if  accompanied  by  the  necessary 
organization,  makes  for  greater  efficiency, 
greater  economy,  and  more  accurate  and  uni- 
form results. 

It  will  be  at  once  seen  that  it  would  be 
an  error  to  place  the  department  in  such  a 
part  of  the  hospital  as  to  make  it  necessary 
for  outdoor  and  dispensary  patients  to  wan- 
der through  the  halls  and  ride  in  the  elevators 
to  reach  the  laboratory.  Again,  it  is  a  hard- 
ship to  trundle  patients  on  stretchers  in  wintry 


PLAN  OF  SMALL  LABORATORY 


223 


gales  and  driving  rain  across  courtyards  to  the 
laboratory.  The  department  should  be  placed 
in  close  proximity  to  the  wards,  the  center  of 
the  hospital's  activities,  so  as  to  make  it  easily 
accessible  to  both  patient  and  attendant.  The 
ground   floor,   is,  therefore,   usually  the  best. 


-e- 


Fig.   305. — Plan   of   medium   sized   x-ray   laboratory 
with  solid  revolving  doors. 


1.  Photographic  room. 

2.  Demonstrating  room. 

3.  Machine-operating  room. 


4.  Examining  room. 

5.  Fluoroscopic  room. 

6.  Waiting  room. 


and  the  site  should  be  as  close  to  the  elevator 
as  is  possible.  In  such  a  location  the  depart- 
ment is  made  accessible  to  all  from  without, 
is  convenient  for  the  administration,  for  the 
wards  and  the  delivery  of  supplies. 

There  are  three  phases  to  the  roentgen  ex- 
amination : 

L  The  making  of  the  plate. 

2.  The  developing  of  the  plate. 

3.  The  reading  of  the  plate. 
Therefore,  there  are  necessary : 
L  The  examining  room. 

2.  The  photographic  dark  room. 

3.  The  demonstration  room. 


Under  certain  conditions,  when  only  one 
large  room  is  available,  it  is  an  error  to  divide 
it  into  small  rooms,  for  it  only  adds  to  the 
general  inconvenience  and  interferes  with  light 
and  air.  One  such  room  may  be  fitted  to  do 
all  the  work  necessary,  as  in  figure  306.  Such 
an  arrangement  undoubtedly  has  inconven- 
iences among  which  are : 

L  The  impossibility  of  utilizing  this  room 
for  radiographic  or  demonstration  purposes, 
while  development  of  plates  is  taking  place. 

2.  The  impossibility  of  developing  the 
plates,  while  examination  or  exposures  are 
being  made. 

But  in  small  laboratories,  where  but  little 
work  is  done  and  definite  hours  for  the  various 
activities  established,  this  arrangement  may 
well  be  adopted.  From  this  simple  arrange- 
ment of  multum  in  parvo,  expansion  and  ex- 
tension may  be  carried  on  to  overcome  the 
disadvantages. 

The  advantages  and  the  necessity  of  an  ad- 
joining  demonstration   room  at  once  become 


Fig.   306. — Plan   of   a   simple  arrangement  of   x-ray 
laboratory  in  one  room. 
A  Desk. 
B  Tube  closet. 
C  Supply  closet. 
D  Transformer. 

E  E  E  Illuminating  boxes  and   files. 
F  Switch  board. 

G  G  Developing,  fixing,  and  washing  tanks. 
H  Plate  closet  and  shelves  for  loading.  . 


apparent.  This  room  should  be  so  placed  that 
it  is  not  necessary  to  cross  the  examination 
room  to  reach  it. 


224 


EELLEVUE  HOSPITAL 


PLAN   OF  SMALL  LABORATORY 


225 


The  disadvantage  of  the  above  siniiile 
plan,  arising  from  the  necessity  of  ceasing 
examination  while  development  is  going  on, 
may  be  overcome  by  the  addition  of  a 
small  dark  room.  This  dark  room  should 
be  placed  as  far  from  the  examination  room 
as  is  consistent  with  comfort,  so  as  to  obviate 
the  necessity  of  covering  its  walls  with  lead 


trolled.  Witliin  this  room  is  also  ]jlaced  the 
interrupterless  machine,  as  the  noise  of  the 
motor  tends  to  alarm  sensitive  patients  and 
children.  The  partition  between  these  rooms 
should  be  covered  with  lead  1/32-1/16  inches 
thick.  If  this  is  not  feasible,  a  booth  (lead- 
lined  )  should  be  constructed,  sufficiently  large 
to  contain  switchboard  and  two  operators. 


Fig.  308. — Radiographic  Room,  Bellevue  Hospital. 


for  the  protection  of  the  plate.  The  demon- 
stration room  may  be  made  to  intervene 
between  the  dark  room  and  the  examination 
room. 

The  best  protection  is  otTered  the  operator 
when  he  is  entirely  out  of  the  room  containing 
the  x-ray  tube.  This  is  accomplished  by 
placing  a  small  room  between  the  demonstra- 
tion room  and  the  examination  room.  We 
may  call  this  the  machine-operating  room, 
inasmuch  as  from  here  the  apparatus  is  manip- 
ulated, the  tube  regulated  and  the  lights  con- 


In  larger  laboratories  it  frequently  becomes 
necessary  to  remove  the  fluoroscopic  apparatus 
to  another  room  in  order  that  these  examina- 
tions may  be  made  without  interfering  with 
the  routine  radiographic  work.  Under  these 
circumstances,  the  fluoroscopic  room  should 
adjoin  the  machine-operating  room  and  the 
examination  room.  In  some  laboratories  the 
vast  majority  of  the  examinations  are  fluoro- 
scopic, the  plate  being  but  supplementary,  for 
purposes  of  record,  and  this  form  of  exam- 
ination is  playing  and  is  destined  in  the  future 


226 


PROTECTION  OF  WORKERS 


to  play  an  important  part  in  the  x-ray  labora- 
tory examinations,  and  will  undoubtedly  di- 
minish the  cost  of  maintenance. 

Finally,  where  a  large  number  of  examina- 
tions are  to  be  made,  a  waiting  room  for  pa- 
tients becomes  absolutely  necessary,  since 
otherwise  considerable  time  is  wasted  waiting 
for  patients  to  arrive  or  be  removed.     This 


Protection 

There  is  one  important  consideration  in  the 
construction  and  planning  of  the  varios-s  rooms 
of  an  x-ray  department  and  this  is  the  protec- 
tion of  the  working  staff,  not  only  from  con- 
stant exposure  to  the  ray,  but  from  the  ill 
eft'ects  of  insufficient  ventilation  and  imperfect 
electrical  conditions. 


Fig.  309. — Fluoroscopy  room  showing  vertical  and  horizontal  apparatus  and  switchboard  for  their  con- 
trol. The  energizing  apparatus  is  in  another  room.  A  dictagraph  system  permits  the  dictation 
of   the   results   of   the   examination  to   a   stenographer  in  a  distant  room. 


room  should  directly  adjoin  the  examination 
and  fluoroscopic  rooms. 

Thus  an  arrangement  which  covers  the 
rooms  desired  in  a  modern  laboratory  will 
have  a  demonstration  room,  dark  room,  ma- 
chine-operating room,  examination  room, 
fluoroscopic  room  and  a  waiting  room,  all  so 
disposed  as  to  be  readily  accessible  and  easily 
controlled  and  supervised. 


\'entilation  of  the  rooms,  particularly  those 
in  which  the  daylight  is  not  permitted  to  enter, 
is  important.  The  tired  feeling  of  which  x-ray 
workers  complain  is  due  to  the  ozone  liberated 
from  the  air  by  the  x-rays. 

Even  with  sufficient  room  and  protection, 
the  roentgenologist  is  still  liable  to  consid- 
erable physical  injury.  He  should  not  confine 
himself  to  the  laboratory  for  the  entire  day. 


PROTECTION  OF  WORKERS 


227 


An  interval  of  one  or  two  hours  should  occur 
between  the  morning  and  afternoon  work, 
during  which  time  he  should  be  in  the  open 
air.  The  room  in  which  the  exposures  are 
made  and  those  which  are,  during  w'orking 
hours,  kept  darkened,  should  be  exposed  to 
the  sunlight  for  a  part  of  each  day  and  thor- 
oughly aired. 


"  It  is  their  duty  to  give  every  protection 
consistent  with  the  kind  of  work  to  be  done. 
Towards  this  end  it  is  the  duty  of  those  in 
authority  to  provide  all  the  necessar}'  means 
of  protection  against  the  ill  efTects  of  the 
rays,  such  as  lead  screens,  opaque  aprons  and 
gloves,  lead  glass  goggles." 

Organic  changes   in   the   skin   and   internal 


Fig.  3iO. — .Another  view  of  fluoroscopy  room  showing  fluoroscopic  chair  arranged  tor  orthofluoroscopic 
examinations.     A   control  board  is  provided   with  this  apparatus. 


The  worker  should  never  forget  that  the 
x-ray  is  a  two-edged  sword,  a  power  for  much 
good,  yet  capable  of  dealing  much  harm  to 
all  those  coming  within  its  reach.  It  is  a  duty 
of  the  hospital  toward  their  roentgen  labora- 
tory appointees  to  see  to  it  that  they  are 
amply  protected  from  any  deleterious  elTects 
of  the  rays.  Kirschberg  quotes  legal  abstracts 
showing  the  duty  of  employer  to  em])loyee  in 
the  protection  of  life  and  health  and  says : 


organs,  particularly  testicles,  ovaries,  spleert 
and  kidneys,  may  restilt  from  such  intermit- 
tent exposure  as  an  operator  nia\-  get  during 
the  course  of  several  years'  work.  Those 
parts  of  the  skin  most  easily  and  commonly 
injured  are  that  of  the  back  of  the  hand  and 
the  extensor  side  of  the  finger,  less  frequently 
the  skin  of  the  face  and  rarely  that  of  the 
chest  or  abdomen.  Of  the  internal  organs, 
the   testicles    and   ovaries   are   the   most    fre- 


228 


PROTECTION 


quently  affected.  Azoosaspermia  may  occur 
which  may  be  temporary  or  may  become  a 
permanent  sterility.  Talengiectasis,  keratoses, 
and  ulcerations  may  result  which  may  become 
very  malignant  and  lead  to  metastasis. 

There  is  also  the  danger  of  electric  shock 
and  even  electrocution,  when  transformers  of 
great  capacity  are  operated  with  controls 
which  tend  to  maintain  a  constant  potential. 
Shearer  believes  that  death  may  result  from 
the  passage  of  a  current  of  one  hundred  mil- 
liamperes  at  only  five  hundred  volts,  if  the 
voltage  be  maintained  for  an  interval.  If  a 
rheostat  control  is  used,  the  formation  of  an 
arc  on  the  high  tension  line  will  result  in  an 
automatic  drop  in  the  high  tension  voltage  but 
with  an  auto-transformer  control  the  high 
tension  voltage  would  be  maintained  by  an 
increase  of  energy  in  the  primary. 

Therefore  in  using  transformers  with  auto- 
transformer  controls  great  care  must  be  taken, 
particularly  during  the  administration  of 
therapy,  where  a  nine  inch  gap  is  maintained. 
An  imperfection  in  the  connections  may  result 
in  dangerous  arcing  to  the  patients  or  opera- 
tor's body.  Shearer  summarizes  the  precau- 
tions to  be  taken  as  follows : 

(1)  All  high  tension  lines  should  be  well 
mounted  so  as  to  prevent  their  sagging,  break- 
ing or  being  brought  in  any  way  near  the 
patient. 

(2)  Overhead  wires  should  be  mounted  at 
least  ten  inches  above  the  head  of  any  person. 

(3)  Milliameters  of  more  than  one  range 
should  be  provided  with  safety  devices  for 
shifting  scale. 

(4)  No  metal  table  should  be  used  where 
the  patient  is  placed  between  tube  and  table, 
especially  in  treatment. 

(5)  There  should  be  no  possibility  of  spark- 
ing from  lines  to  patient  or  operator,  when 
using  a  vertical  fluoroscope  or  trochoscope. 

(6)  No  unused  leads  or  connecting  wires 
should  be  left  connected  with  the  high  tension 
lines.  Do  not  leave  a  vertical  fluoroscope  con- 
nected when  not  in  use. 

(7)  A  quick-acting  circuit  breaker  should 
be  mounted  in  the  primary  circuit  of  the  trans- 


former and  adjusted  to  open  just  above  the 
maximum  power  needed  in  gastro-intestinal 
work.  In  fact,  one  might  be  devised  to  open 
on  smaller  current  as  the  tube  voltage  is  raised. 

(8)  The  Coolidge  filament  battery  or  trans- 
former must  be  regarded  as  a  part  of  the  high 
tension  line  and  a  source  of  danger,  unless 
properly  protected  and  mounted. 

Adequate  protection  is  particularly  impor- 
tant in  war  work,  because  of  the  demands 
made  upon  individual  operators.  This  pro- 
tection is  most  practically  obtained  by  encas- 
ing the  hands  and  body  of  the  operator  with 
protective  material,  preferably  pliable  lead 
rubber.  For  the  protection  of  the  head,  face 
and  eyes,  a  rubber  mask,  containing  lead  glass 
spectacles  may  become  necessary.  Nogier  has 
devised  a  metal  helmet  with  a  movable  visor 
of  lead  glass.  This  helmet  is  similar  to  the 
trench  helmet,  the  front  piece  of  lead  glass, 
reaching  down  to  the  chin,  protecting  the  hair, 
face,  eyes  and  two  side  pieces  of  metal  for 
protection  of  the  ears.  The  front  part  of  lead 
glass  may  be  closed  and  opened  by  means  of 
a  hinge.  For  protection  of  the  trvuik,  the  lead 
rubber  apron  is  sufficient  but  must  be  ample 
enough  to  protect  the  body  at  the  sides.  For 
the  protection  of  the  legs,  lead  rubber  leggings 
have  been  employed.  All  these  protections 
are  of  no  avail  if  the  operator  has  not  trained 
himself  to  make  the  examination  quickly  and 
has  constantly  in  mind  the  danger  to  which 
he  subjects  himself.  The  regulations  sug- 
gested by  Nogier  for  this  discipline  are  as 
follows : 

1.  The  roentgenologist  must  never  make 
any  examination  without  an  apron,  gloves  and 
spectacles :  or  better  still,  he  should  wear  the 
protective  helmet. 

2.  The  examination  should  be  made  with 
the  smallest  possible  opening  of  the  dia- 
phragm. 

3.  The  roentgenologist  ought  never  to  pal- 
pate by  hand  for  a  foreign  body  under  the 
screen,  even  when  employing  an  opaque  glove. 

4.  The  palpation  must  be  done  with  a 
metallic  instrument  placed  on  the  end  of  a 
wooden  handle. 


EQUIPMENT  OF  ROOMS 


229 


5.  In  every  examination  the  tube  should  not 
be  energized  except  at  the  exact  moment  of 
use.  For  this  purpose  the  foot  switch  should 
be  employed. 

6.  The  screen  should  never  be  held  in  the 
hand  but  by  a  protected  handle  fixed  to  the 
frame  of  the  screen. 

7.  When  it  is  necessary  to  remove  the 
gloves    for     more     delicate     localization,    the 


genologist  ought  to  employ  a  small  Spanish 
wall,  lined  with  lead,  to  protect  the  knees  and 
the  legs. 

Eqiiipniciit 

The  assembling  of  the  equipment  of  an 
x-ray  laboratory  presents  many  problems.  To 
the  uninitiated  the  apparent  difference  of 
opinion  among  workers  alone,  based  on  their 


Fig.  311. — Serial  room.     The  apparatus   for  making  teleradiographic  examinations  is  shown  on  the  right. 

--\t   the  left  is  the  vertical   serial  apparatus. 


roentgenologist  must  never  hold  the  pencil  for 
marking  on  the  glass  or  the  patient  directly  in 
his  hand  but  should  employ  a  pencil  holder 
with  a  protective  cuft". 

8.  If  the  Coolidge  tube  is  used  it  should  be 
remembered  that  the  rays  are  emitted  pos- 
teriorly to  the  anticathode,  and  that  the  roent- 
genologist is  therefore  subjected  to  more  ex- 
posure than  with  the  use  of  the  gas  tube. 

9.  If  there  are  nuinerous  fluoroscopic  ex- 
aminations in  the  vertical  position,  the  roent- 


varied  experience,  is  puzzling  and  with 
the  manufacturers  displaying  a  wide  range  of 
variety  in  devices  intended  to  simplify  the 
work,  the  problem  of  the  selection  of  equip- 
ment becomes  an  exceedingly  difficult  one ; 
for,  who.  indeed,  shall  decide,  when  experts 
disagree  ? 

And  yet.  -when  analyzed,  it  will  be  found 
that  the  diff'erence  of  opinion  among  workers 
is  not  so  great,  but  that  there  is  a  striking 
identity  of  ideas  among  the  worthiest  repre- 


230 


EQUIPMENT  OF  ROOMS 


sentatives  of  this  specialty.  The  assembling 
of  the  equipment  of  a  laboratory  is  strictly  the 
business  of  the  roentgenologist,  and  neither 
the  inexperienced  layman  or  medical  man  is 
competent  to  perform  the  task,  for  there  ex- 
ists the  possibility  that  price,  polish  or  paint 
may  appeal  with  greater  force  than  insula- 
tion, commutation  or  efficiency.  Nor  does  it 
take  any  extensive  experience  to  teach  that 
simplicity  in  construction  and  singleness  of 
purpose  is  a  desideratum  in  apparatus,  in 
other  words,  that  it  is  better  to  have  an  ap- 
paratus which  does  but  one  thing,  and  that 
simply  and  well,  than  one  which  serves  many 
purposes,  but  serves  none  of  them  properly. 

The  details  of  the  construction  of  the  various 
apparatus  and  the  advantages  or  disadvantages 
of  this  or  that  particular  type  of  machine  or 
tube  have  been  discussed.  The  furnishing  and 
equipment  of  the  various  rooms  of  a  medium- 
sized  laboratory  will  be  outlined. 

Examining  Room 

The  examining  room,  being  the  room  in 
which  the  plate  examinations  are  made,  holds 
(with  the  contents  of  the  machine-operating 
room)  the  essential  apparatus  for  the  radio- 
graphic (plate)  examination.  It  is  necessary 
that  this  room  measure  at  least  one  hundred 
and  seventy-five  square  feet.  The  walls 
should  not  be  painted  black,  as  it  unnecessarily 
increases  the  gloom  of  the  room.  A  light 
bluish  green  tint  serves  the  purpose,  if  the 
room  is  to  be  darkened. 

Table 

The  table  should  be  low,  not  too  narrow, 
firm  and  easily  movable.  The  table  top  should 
have  a  tunnel  underneath  for  the  reception  of 
pan  for  holding  plates  or  cassettes.  The  table 
top  should  be  adjustable  from  thirty-one  to 
sixty  inches,  preferably  by  means  of  a  system 
of  gearing  adjustable  by  a  crank  handle  placed 
on  the  base  of  the  table,  just  above  the  castered 
legs. 

A  suitable  breaking  system  should  be  affixed 
to   hold  the   table  "top   firmly   in   any   height. 


Sufficient  clearing  must  he  left  in  the  tunnel 
to  permit  shifting  of  the  pan  which  should  be 
double  roller  bearing,  moving  in  tracks,  and 
self-centering,  when  two  aluminum  cassettes 
measuring  eighteen  and  three-quarter  inches  by 
fifteen  and  three-quarter  inches  by  five-eighths 
inches  are  fastened  thereon.  The  legs  of  the 
table  consist  of  steel  tubing,  one  of  which 
should  bear  a  scale  to  indicate  the  degree  of 
elevation.  The  shifting  of  plates  underneath 
the  table  top  should  be  made  by  means  of  a 
spiral  spring  and  an  adjustable  air  cushion 
shock  absorber.  One  .  end  of  the  table  top 
should  be  provided  with  a  swivelled  head  rest 
tunnel  for  8  x  10  inch  plates.  In  some  of  the 
tables  on  the  market  the  table  top  may  be 
raised  vertically  and  permits  stereoscopic  ex- 
posvires  in  the  vertical  position.  This  is  an 
undoubted  advantage.  Then,  too,  by  means 
of  a  board  hooked  over  its  upper  edge  to 
which  single  plates  may  be  attached,  chest 
or  stomach  plates  may  be  made  in  the  vertical 
position. 

Tube  Stands 

There  are  numerous  tube  stands  on  the 
market,  but  the  majority  of  them  are  either 
too  clumsy  or  too  flimsy.  The  mechanism  of 
the  stand  should  be  simple,  its  movements 
smooth  and  easy,  facilitating  accurate  and 
quick  adjustment  for  stereoscopy.  It  should 
permit  of  gradual  but  firm  compression  and 
be  sufficiently  heavy  to  prevent  vibration.  The 
clamps  of  the  stand  holding  the  tube  should 
be  of  wood ;  the  clamp  should  be  capable  of 
being  simply  and  quickly  adjusted  so  as  to 
save  time  in  changing  tubes.  When  the  ser- 
vice is  entirely  an  outdoor  one  and  patients 
are  able  to  walk  to  the  table,  a  tube  stand 
permanently  attached  to  the  table  may  be  con- 
venient :  but  when  it  is  necessary  to  make  ex- 
posures of  helpless  patients  directly  upon  the 
carriers  in  which  they  are  brought  to  the  de- 
partment, the  movable,  isolated  tube  stand  is 
most  convenient,  as  it  permits  of  ready  adjust- 
ment over  the  stretcher.  • 

This  room  should  also  contain  a  tube  closet, 
the  tubes  being  hung  on  curved  wires  fastened 


EQUIPMENT  OF  ROOMS 


231 


to  its  back.  The  closet  should  contain  one  or 
more  incandescent  hghts.  'J"he  doors  of  this 
closet,  as  of  all  others  within  the  department 
should  be  sliding.  Another  closet  for  holding 
cones,  sandbags,  head  clamps,  compressions 
ball,  loofah  sponge,  and  other  accessories ;  a 
small  shelf  in  one  corner  for  the  fan  and  a 
screen  with  chairs  behind  it,  where  patients 
can  undress,  completes  the  equipment. 

Where  there  is  much  work  to  be  done,  the 
radiographic  unit  of  tube  stand  and  table  may 
be  duplicated.  Thus,  a  plate  holder,  consist- 
ing of  a  counterweighted  arrangement  for 
holding  the  plate,  may  be  added  for  upright 
chest  and  stomach  examinations;  and,  if  de- 
sired, a  third  unit,  consisting  of  a  small  table 
for  the  examination  of  the  upper  extremities. 
^M^en  these  units  are  ready  for  operation,  the 
current  of  the  energizing  apparatus  may  be 
switched  rapidly  from  one  unit  to  another  by 
means  of  a  high-tension  switch  and  the  trolley 
system,  and  the  work  performed  with  celerity. 

Machine  Room 

The  machine-operating  room  is  like  the  con- 
ning tower  of  a  battleship,  from  which  all  the 
activities  of  the  department  are  controlled. 
In  it  is  placed  the  energizing  apparatus.  An 
energizing  apparatus  sufficient  to  meet  all  the 
requirements  of  a  general  service  should  have 
such  potential  as  to  permit  the  making  of  a 
plate  of  the  chest  with  the  proper  tube,  without 
an  intensifying  screen,  in  such  a  fraction  of  a 
second  as  will  give  a  sharp  negative,  without 
the  necessity  of  requesting  the  patient  to  hold 
his  breath. 

There  are  several  excellent  varieties  of  in- 
terrupterless  machines  on  the  market.  The 
most  adaptable  apparatus  should  be  selected; 
a  transformer  with  a  variable  induction  pri- 
mary is  preferable,  as  it  permits  of  a  great 
orientation  of  the  potential  to  the  vacuum 
of  the  tube.  Until  recently  the  coil  was  the 
most  commonly  used  form  of  energizing  ap- 
paratus, but  of  late  this  has  been  replaced  in 
most  laboratories  by  a  high-tension  trans- 
former of  the  interrupterless  type. 

In  deciding  the  type  of  apparatus  required 


for  a  laboratory  the  variety  of  the  work  must 
be  considered.  If  the  work  is  such  that  no 
speed  in  exposure  is  required,  as  for  the  head 
or  bones,  then  a  coil  capable  of  operating  tubes 
of  high  vacuum  may  be  selected.  An  excel- 
lent coil  may  be  purchased  at  one-third  the 
price  of  a  transformer.  When,  however,  the 
service  is  large  and  general,  and  speed  is  re- 
quired, as  in  the  making  of  chest,  heart  or 
gastro-intestinal  examinations,  the  trans- 
former is  preferable. 

Through  the  lead-covered  wall,  which  sep- 
arates this  room  from  the  adjoining  examina- 
tion room,  the  high  tension  current  is  carried, 
by  means  of  insulated  tubes,  to  the  trolley 
system  in  the  examination  room.  With  the 
aid  of  a  lead-glass  window  easy  inspection  of 
the  examining  room  should  be  possible.  In 
this  wall  is  also  placed  a  megaphone  for  speak- 
ing to  the  patient  in  the  examining  room.     - 

A  desk  and  a  lead-lined  box  with  two  com- 
partments for  holding  plates  complete  the 
equipment  of  this  room.  In  the  opposite  wall 
between  this  room  and  the  dark  room,  a  win- 
dow with  a  solid  revolving  door  should  be 
placed,  which  will  permit  screen  and  plates  to 
be  passed  in  and  out  of  the  dark  room  without 
the  necessity  of  entering. 

Fluoroscopic  Room 

The  fluoroscopic  room  should  be  of  the 
same  size  as  the  radiographic  room.  The 
lighting  of.  this  room  is  important  and  should 
be  such  as  to  permit  the  eye  to  become  rapidly 
sensitized.  The  indirect  or  reflected  lighting 
system,  using  an  inverted  bowl  of  greenish 
hue  reflected  from  a  white  ceiling,  and  having 
the  walls  of  a  bluish-green  color,  gives  suf- 
ficient light  of  the  proper  sort  and  rests  and 
sensitizes  the  eye  to  the  color  of  the  cyanide 
fluorescent  screen.  The  more  rapidly  the  eye 
is  sensitized,  the  more  accurate  and  speedy  is 
the  examination.  In  a  room  of  this  sort,  as 
in  the  photographic  dark  room,  where  daylight 
must  be  excluded,  artificial  ventilation  is 
essential  by  one  of  the  many  forms  of  ven- 
tilators. 

Properlv  equipped  and  utilized,  the  fluoro- 


232 


EQUIPiMENT  OF  ROOMS 


scopic  room  is  the  most  valuable  adjunct  of 
the  x-ray  laboratory.  Not  only  does  it  make 
possible  a  rapid  diagnosis,  but  it  permits  the 
rejection  of  normal  material  and  saves  much 
useless  radiographic  work.  In  gastro-intes- 
tinal  and  chest  work  this  method  of  examina- 
tion is  indispensable. 

The  equipment  of  this  room  consists  of 
apparatus  for  examining  patients  both  in  the 
horizontal  and  vertical  position.  There  are 
some  fluoroscopic  statives  which  are  capable 
of  such  manipulation  as  to  permit  the  exam- 
ination of  patients  in  both  positions,  but  these 
are,  as  a  rule,  difficult  to  handle,  clumsy,  ex- 
pensive and  give  insufficient  protection. 

Of  all  the  apparatus  in  the  x-ray  laboratory 
the  horizontal  fluoroscope  or  trochoscope  is 
perhaps  the  most  important  and  useful.  The 
trochoscope  may  be  utilized  not  only  for 
fluoroscopic  examinations  in  the  horizontal 
position,  but  also  for  plate  work  with  the  aid 
of  a  tube  stand,  the  stereoscopic  work  being 
done  by  means  of  an  attached  tunnel  plate 
holder  which  may  be  suspended  from  the  side 
when  not  in  use.  In  fact,  in  the  small  labora- 
tory it  is  preferable  to  obtain  and  use  such  a 
trochoscope,  with  a  hinged  solid  top,  as  the 
regular  examining  table. 

There  are  many  excellent  vertical  fluoro- 
scopic statives  on  the  market  which  embody 
all  the  requisites  of  protection,  simplicity  of 
movement  and  adjustment.  With  the  vertical 
apparatus,  patients  may  be  examined  in  the 
standing  or  sitting  position.  The  ideal  ener- 
gizing apparatus  for  fluoroscopic  work  is  an 
induction  coil  operated  by  a  mercury-gas  in- 
terrupter, and  the  ideal  tube  is  a  properly 
seasoned  one  with  an  air-regulating  attach- 
ment. ^^'hen  a  transformer  is  the  energizing 
source,  the  Coolidge  tube  gives  the  most  satis- 
faction  for  fluoroscopic  work. 

This  room  should  be  also  provided  with  a 
lead-covered  box  of  sufficient  size  to  hold  14 
x  17  plates.  A  dressing  screen  on  one  corner 
and  a  table  for  the  bismuth  preparation  in  the 
opposite  corner,  a  revolvable  chair,  leaded 
gloves  and  glasses,  lead-lined  aprons,  wooden 


spoons  for  palpation,  complete  the  equipment 
of  this  room. 

Demonstration  Room 

In  the  demonstration  room  are  placed  the 
illuminating  boxes  for  the  viewing  of  the 
plates,  the  Wheatstone  stereoscope,  the  files 
and  the  office  furniture. 

Large  boxes  may  be  constructed,  covering 
the  walls  of  the  room.  These  illuminators  are 
set  on  cabinets,  having  two  files  of  compart-, 
ments  for  filing  plates. 

The  stereoscopic  viewing  apparatus  should 
consist  of  two  illuminating  boxes,  adjustably 
mounted  upon  all  metal  carriers,  which  engage 
an  accurate  rack  and  pinion  mechanism  in 
such  a  manner  as  to  enable  the  operator,  by 
manipulating  a  conveniently  located  operating 
handle,  to  cause  the  illuminating  boxes  to 
approach  or  recede  to  and  from  each  other 
in  exact  unison. 

The  illuminating  boxes  are  to  hold  negatives 
of  any  size  up  to  fourteen  by  seventeen  inches, 
on  each  of  its  three  or  four  sides,  and  be 
equipped  with  opaque  water  and  heat  proof 
curtains,  mounted  on  spring  rollers  so  ar- 
ranged that  the  illuminating  opening  may  be 
quickly  and  conveniently  adjusted  to  any  size 
negative.  The  light  should  be  diffused  by 
blazed  or  double  ground  glass.  By  means  of 
a  small  rheostat  attached  to  each  box  the 
intensity  of  the  light  is  controllable. 

The  reflecting  mirrors  should  be  mounted 
at  right  angles  to  each  other,  in  an  all  metal 
framework,  which  in  turn  rests  upon  two 
parallel  steel  rails,  so  that  the  mirrors  may 
be  slid  transversely  across  the  stereoscopic 
frame  to  any  point  desired. 

The  wings  or  light  shields  should  be 
mounted  on  the  mirror  frame. 

A  graduated  scale  is  to  be  provided  to  note 
the  exact  position  of  the  illuminating  boxes 
in  relation  to  each  other,  and  to  the  reflecting 
mirrors. 

An  arrangement  of  the  fronts  of  the  illu- 
minating boxes  should  be  such  as  to  suffi- 
ciently insulate  the  plates  from  the  heat. 

The   carriers   upon   which   the    illuminating 


EQUIPMENT  OF  ROOMS 


233 


boxes  rest  should  be  of  steel,  provided  with 
small  wheels  or  rollers  to  facilitate  a  free 
uniform  movement  of  the  illuminators  along 
the  rails.  The  illuminating  boxes  should  be 
rotated  or  swivelled  and  be  completely  remov- 
able, as  separate  diagnostic  boxes. 

Filing  and  Record  Room 

The  most  convenient  method  of  filing  plates 
is  in  numerical  order,  the  plates  being  separate 
from  each  other  by  filing  guides.     The  dupli- 


cate reports  filed,  one  according  to  name  of 
patient  and  the  other  according  to  a  disease 
index  should  be  kept  in  letter  files. 

Photographic  Dark  Room 

The  plans  of  the  equipment  above  outlined 
may  undergo  considerable  amplification  in 
order  to  meet  the  requirements  of  large  labora- 
tories. Duplication  of  rooms  and  apparatus 
then  becomes  necessary  in  order  to  permit  a 
lare;e  staff  to  work. 


GENERAL  INDEX 


Abdomen,  radiography  of,  189-194 

Absorption   estimation   of   the   x-rays,   78,   195 

Accessory   sinuses,    radiography   of,    153. 

Accumulators,  8,  9,  49 

Acetabulum,  radiography  of,  172 

Acromio-clavicular  joint,  radiography  of,  178 

Activated  Coohdge  tube,  85. 

Activated  Gas  tube,  appearance  of,  82 

Advantages  of  CooHdge  tube.   130 

Aeroplane    radiological    unit.    55 

Air-cooled  tube.  65 

Air  regulator,  65 

Alternating  current,   14,   17 

Alternating  current,  coil  outfit.  33 

.A.1ternating  current,  commutation  of,  19 

Alternating  current  conversion,  method  of,   15,   iS 

Alternating  current  curves,  16,  17 

Alternating  current  generator,  14 

Alternating  current  motors.  15 

Alternating  current  periodicity,  17 

Alternating  current  supply,  17 

Aluminum  cathode,  62.  80 

Aluminum  filters.  102,  116 

Ampere.  5 

Ampere  hours.  9 

Amperemeter,  20-22 
Coil  outfit  of,  32 
Hot  wire,  22 
Varieties  of,  22 
Amperemeter  for  Coolidge  tube  testing,  129 
Ankle,  radiography  of,   175 
Anode,  7,  10 
double,  62 
glass  sleeve  for,  64 
Anode,  Coolidge  tube,  68 
Anode.  X-ray  tube,  62,  63.  86 
Arm.  radiography  of,  181 
Armature.  11.  15 
Army  wagon,  x-ray,  55 
Atoms,  attraction  and  repulsion  of,  2 
Auto-transformer  control,  42.  43.  44 
Axioms,  radiological.   142,   143.   144,   145 
Axial  ray.  1 18 

B 

Backing  of  plate  by  lead,  131 
Barium,  gastrq-intestinal  tract.  191 
Base  of  skull,  radiography  of.  151 


Battery 

care  of,  g 

charging  of.  g 

Edison,  g 

requisites  of,  8 

storage,  8 

use  of  with  portable  apparatus.  49 

voltaic,  7,  8 
Bauer  air  valve  regulator,  65,   116 
Bauer  qualimeter,  95,  96 
Bedside  unit,  U.  S.  Army,  52 
Bellevue  Hospital  X-ray  Laboratorj',  224 
Benoist  penetrometer,  97 
Biological  eflfects.  X-ray,  79 
Biroentgenographic  apparatus,   136 
Bismuth  subcarbonate,  190 
Bladder,  urinary,  radiography  of,  194 
Bladder,  gall,  radiography  of,  191 
Booster,  41,  44 
Bordier  meter,  107 
Bowen's  ruler.  198 
Bragg,  y- 

Brown  Percy,  chair  for  radiography  of  the  skull,  149 
Bromide  of  silver  plate,  137 
Brushes,  motor.   15 
Bucky  diaphragm,  91 
Bulb.  X-ray  tube.  62 
Bulb,  X-ray,  variation  in  size,  88 
Bulb,  Lindeman  glass.  88 


Cabinet  for  filing  lantern  slides,  215 

Cabinet,  interrupterless  apparatus,  41 

Camion.  American,  54 

Carbon  penetrability,  78 

Care  in  handling  plates,  137 

Care  of  motors,  36 

Care  of  storage  batteries,  9 

Carpal  bones,  radiography  of.  183 

Cassettes.  138 

Cathode.  10 

Cathode.  Coolidge  tube,  68 

Cathode,  discharge,  75 

Cathode  rays,  2.  76 

Cathode,  X-ray  tube.  62.  80 

Cathode  rays,  characteristics  of.  76 

Cathode  stream,  75.  83 

Cells,  battery.  7.  8 

Cells.  Voltaic.  7.  8 

Central  ray.  118,  iig 


[235] 


236 


INDEX 


Centric  arrangement,  140 
Centric  and  eccentric  views,  141 
Centrifugal  interrupter,  28 
Cervical  spine,  164 
Characteristic  rays,  89,  90 
Characteristics  of  good  radiograph,  195 
Charge,  negative,  2 
Charging  by  contact,  3 

by  induction,  4 

by  storage  batteries,  8,  49 
Choke  coil,  13 

Chemical  efifects  of  electricity,  10 
Chemical  effects.  X-ray,  79 
Chemical  rectifiers,  19 
Chest,  185,  188 

Chest,  radiography  of,   185,  188 
Chest,  stereography,   132 
Christen  meter,  97,  98 
Christen-Hirsch   penetrometer,   99 
Chrome-alum  fixing  bath,  209 
Chromo-radiometer,  107 
Circuit,  closed,    15 

Circuit,  closed,  rotated  between  magnetic  poles,  14 
Circuit,  closed,  on  transformer,  35 
Circuit,  Coolidge  tube,  69 
Circuit,  electric,  15 

grounded.  16 
Circuit,  magnetic,  11 
Circuit-Ohm's  law,  S 
Circuit,  open,  15 

Circuit,  primary  and  secondary,  31 
Clavicle,  178 

Clavicle,  radiography  of,  178 
Closed  core  transformer,  23,  24,  34 
Coil  induction,  23,  24 
Coil,  sparking  distance,  25 
Coil,  characteristics  of  discharge,  45 
Coil,  switchboard,  31 
Coil  outfit,  30 

Colon,  radiography  of,  191,  192 
Commutator,  15 

in  interrupterless  apparatus,  36-39 
Commutation  disc,  37 
Commutation,  rotating  arm,  40 
Cominutation.  alternating  current,   15,   18,  37 
Compression,  in  radiography,  14S 
Compression  frame  for  stereography,  132 
Condensers,  26 
Conductors,  3 

moving  with  stationary  flux,  12 

moving  with  variable  flux,  13 

stationary  and  variable  flux,  12 
Connection,  coil  outfit,  32 
Connection,  Coolidge  circuit,  71 
Connection,  high  tension,   122 

parallel,  8 

series,  8 


Connections  of  X-ray  tube,  122,  123 
Constant  direct  current,  16,  17,  18 
Continuous  direct  current,  16,  17,  18 
Contrast  in  plate,  199 
Control,  interrupterless  apparatus,  42,  44 
Control,  rheostat,  42 

disadvantages  of,  42 
Converter,  motor,  36 
Converter,  rotary,  19 
Converter  unit,  46-48 

Composition  of  rectifier  of,  46 

Difiference  between  this  and  old  form,  46 

Case  of,  47 

Control  panel  of,  47 

Control  of  voltage  of,  47 

Switchboard  of,  47 

Use  of  voltmeter  of,  47 
Coolidge  circuit,  69 
Coolidge  circuit  connection,  71 
Coolidge  equipment,  129 

Coolidge  filament,  methods  of  heating,  67-69 
Coolidge  focal  spot,  71 
Coolidge  tube,  48,  68 

activated,  85 

advantages  and  disadvantages  of,  130 

fluorescence  of,  71 

fluoroscopy,  "/Z,  116 

metal  deposit,  70 

radiator  type,  71 

regulation    methods   of    126-128 

requisites  of,  129 

technique  of,  128 

as  rectifier,  71 

tell  tale  device,  130 

testing  of,  127 

varieties  of,  yi 
Cooper  Hewitt  arc  light  as  commutator,  19 
Cooper  Hewitt  lamps,  215 
Copper  in  anti-cathode,  '}, 
Copper  element  in  voltaic  cell,  7 
Coracoid  process,  radiograph  of,  153 
Core,  23,  24 
Corpuscular  rays,  89 
Corona  losses,  123 
Coulomb,  5 

Coccyx,  radiography  of,  168 

Cranial   and  orbital  cavity,  radiography  of,   153 
Crookes  dark  space,  60 
Crookes  or  gas  tube,  60,  61 
Crookes,  Sir  William,  56 
Current,  4,   15 

Alternating,  characteristics  of,  16,  17 

alternating  commutation  of,   18 

alternating  cycles,   18 

alternating  interrupter,  33 

alternating  periodicity,   17 

Continuous,  7,  14,  23 


INDEX 


237 


control,  5 

Direct,  15,  17,  23 

Electric,  2,  15 

Energizing,  23 

Extra,  13 

for  Coolidge  filaments,  69 

Galvanic,  7 

high  tension,  23 

Induced,   11,  12 

Inducing,  23 

inverse,  91,  92 

low  tension  transformation  into  high  tension,  23 

Oscillating,  characteristics  of,   16,  17 

Primary,  31 

various  devices  for  purpose  of  interruption, 

25 

Production  of,  13,  14 

Properties  of,  16 

Pulsating,  characteristics  of,  16,  17 

saturation,  70 

time,  strength  and  direction  of,  17 
Cylinder  diaphragm,  88 
Cylinder  for  x-ray  tubes,  85 

D 

Delco-light  generator,  50,  51 

Dangers  in  X-ray  work,  226,  229 

Dark  room,  requirements  of,  207 

Darwin,  TJ 

Definition  in  radiography,  197 

Definition  of  shadow,  145 

Demonstration  room,  233 

Determination  of  polarity,  49 

Determination  of  vacuum  of  tube,  124,  125 

Determination  of  vertical  ray,  118 

Developer  action,  207,  208 

Developing  formula,  207 

Developing  solution,  207,  208 

Developing  of  photographic  plate,  207,  208,  209 

Development,    duration    of,    210 

Development  tank,  209 

Diaphragms,  88 

Iris,  87 

Rectangular,  87 
Diaphragming  x-ray  tubes,  85 
Di-electric,  27 
Di-electric  gas,  27,  29 
Di-magnetic  substances,  11 
Dip   type  interrupter,  28 
Direct  current,  18 

Direct  current   generator,    principles   of,    14 
Direct  continuous  current,   16,   17 
Direct  constant  current,  16,  17 
Direct  pulsating  current,   16,   17 
Director  and   his   duties,  219 


Disintegration  of  metal  by  cathode  rays,  76 

Distance  from  anticathode  to  plate,  196 

Distance  of  tube  plate,   196 

Divergent  ray,  118 

Dorsal  spine,  165,  166 

Dorsal  spine,  radiography  of,  166 

Dorso-ventral,  first  oblique,  140 

Dorso-ventral,  second  oblique,  140 

Dosage,  estimation  of,   100 

Dosage,  method  of  Holznecht,  107 

Double   trochoscope,    113 

Drying  of  films,  211 

Drying  and  fixing,  211 

Drying  of  plates,  211 

Duration  of  development,  210 

Dynamos,  13 

connection  of,  15 

E 

Eccentric  arrangement,  141 
Eccentric  and  centric  views,  141 
Efficiency  of  transformer,  35 
Elbow,  181 

Elbow,  radiography  of   181 
Electricity,  manifestation  of,  I 

definition  of,  i 

effects  of,  9 

forms  of,  3 

power  of,  6 

rate  of  flow,  5 
Electric  charge,  destruction  of,  61 
Electric  circuit,  7 
Electric  connections,  4 

properties  of,  16 
Electric  current,  4,  15 
Electric  fields,  3 
Electric  forces,  lines  of,  3 
Electric  magnets,  5 
Electric  measuring  instruments,  19 
Electrolyte,  6,  7 
Electronic  motion,  4 
Electronic  torrents,  2 
Electro-magnet,  12 
Electro-magnetic  induction,  25 
Electro-motive  force,  11 

development  of,  3 

by  chemical  action,  6 

grounded,  16 

short-circuited,  16 

sine-wave   diaphragm,   17 

value  of,  14 
Electro-motive  force,  counter,  13 
Electro-static  meter,  22,  96 

Electro-static  charges  of  walls  of  x-ray  tube,  83 
Electrode,  position  of,  7 


238 


INDEX 


Electrons,  i,  8i 

characteristics  of,   I 

electrical  charge  of,  i 

fast  moving,  2 

in  matter,  2 

in  rotation,  3 

radio-active  atoms  of,  2 

repulsion  power  of,  i 

slow  moving,  2 

streams  of,  2 

theory  of,  I 

weight  of,  I 
Electron  flow,  2 

Electron  stream,  focusing  of,  80 
Electron  tubes,  68 
Equipment  for  Coolidge  outfit,   129 
Equipment  for  portable  outfit,  54 
Equipment,  rooms  of  X-ray  laboratory,  229-233 
Equipment,  X-ray  laboratory.  218 
Esophagus.  188,  189 
Examination,  the  fluoroscopic,   117 
Examination  of  oblique  diameters,  140 
Examination  of  plate,  213 
Examination  of  plate  by  reflected  light,  214 
Examination  of  plate  by  transmitted  light,  213 
Examination  of  stereo-plates,  215 
Eccentric  views,   140 
Exhaustion  of  x-ray  tube.  60 
Exposure,  the.  IQS 
Exposure,  factors  governing,  193 
Exposure  tables,  200-206 

Factor  system,  200 
Penetration  method,  201-203 

Coolidge  tube,  204 

Gas  tube.  235 
Exposure  timing.  197 
Extra  current.  13 
Extraoral  examination  of  teeth.  161.  162 

F 

Factor  system  of  exposure.  200 

Factorial  development.  210 

Faraday,    12,   56 

Faraday  dark  space,  56 

Faraday  ring.  23 

Femur,  radiography  of  shaft  of,  172 

Fibula,  radiography  of,  175 

Field  magnet,  15 

Filament.  Coolidge  tube,  68 

methods  of  heating,  67-69 
Filament  current,  measurement  of,   129 
Filament,  regulation  of,  69-129 
Filing  envelopes  and  cassettes,   138 
Films,  method  of  drying,  211 
Filtration  in  relationship  to  half  absorption  value,  102 


Fitzeau,  25 

Fixing  and  drying,  211 

Fixing  solution,  209 

Fluoroscopy,   113  *• 

magnification,  117 

palpation,  117 

protection,  116 
Fluoroscopy,  basis  of,  TJ 
Fluoroscopy,  protectional  devices,  116 
Fluoroscopy,  ray  quality  and  quantity  of,  116 
Fluoroscopy,  requisites  of  successful,   113 
Fluoroscopy,  stereoscopic,   120 
Fluoroscope,  combination     horizontal     and     vertical, 

114 
Fluoroscope,  operating,  115 
Fluorescence,  cathode  rays,  76 
Fluorescence,  x-rays,  78 
Fluoroscopic  examination,  117 
Fluoroscopic  image,  tracing  of,  114 
Fluoroscopic  room,  233 
Fluoroscopic  screen,  114.  151 
Fluoroscopic  statives,  113 
Fluoroscopic  switchboard,   117 
Flux,  magnetic.  11 

Flux,  moving  and  stationary  conductor,  12 
Flux,  stationary  and  moving  conductor,  12 
Flux,  variable  and  moving  conductor,  13 
Focal  point,  Coolidge,  70 
Focal  point  gas,  85,   196 
Focal  point  of  target,  83,  84 
Focal  point  tests,  87 
Fogging  photographic.  199 
Foot,  176 

Foot,  radiography  of.   176 
Forearm.  182 

Forearm,  radiography  of.  182 
Frederick.  ~y 

Frontal  bone,  radiography  of.  151 
Frontal  sinuses,  radiography  of,   153 
Furstenau.  75 
Fuses,  10 


Gaede,  60 

Galvanic  cells,  6,  7 
Galvanometer,  20 

especially  constructed,  20 
Gall  bladder,  191 

Gall  bladder,  radiography  of.   191,   192 
Gas,  di-electric,  29 
Gas  engine  and  dynamo,  50 
Gas  tube,  activated,  appearance  of,  82 
Gas  tube  regulation,  65,   125 
Gas  tube  testing,  124 
Gastro-intestinal  tract,  190 

Gastro-intestinal  tract,  radiography  of,   189-191 
Geissler,  56 


INDEX 


239 


Generators,  alternating  current,  12 

Generators,  electric,  13 

Generators,  principle  of  induction,  14 

Generating  system,  17 

Gleno-huineral  joint,  radiography  of,  179 

Grounding.  3 

Grounding,  accessory  anode,  123 

secondary  winding,  123 
Grounding  to  prevent  static  discharges,   124 

H 

Hampson  meter,   108 

Hampson's  method,   108 

Hands,  183,  184 

Hands,  radiography  of,   183.  184 

Head,   148-154 

Head,  radiography  of,  148-154 

Heat  by  cathode  rays,  76 

Hegener  mirror  stereoscope,  216 

Helix.  12 

Hertz,  57  , 

Heterogeneous  rays.  89 

Hewett-Cooper  Lamps.  215 

High  tension  connections,  122,  123 

High  tension  leakage,  123 

High  tension  rectifying  switch,  converter  unit,  46 

High  tension  system,  wire,   123 

High  tension  wiring,  123 

High  tension  voltages,  4 

Hip,  171 

Hip.  radiography  of,  171 

Holzknecht  meter,  107 

Horizontal  fluoroscopic  stative,  232 

Horsepower,  6 

Hot  cathode,  68 

Humerous.  radiography  of,  181 

Hydrogen  ions,  5 

Hj'drogen  tube.  65 

Hj'posulphite  solution,  209 


Ilium,  radiography  of,  169 
Illuminating  boxes,  213.  21s 
Immobilization.   145,  146 
Immobilization  apparatus,  head,  149 
Immobilization,  teeth  examination,  155 
Inductance,  variable  control  of,  42 
Induction,  3 
Induction  coil,  23,  24 

action  of,  25 
Induction  action  temporary  magnet,  13 
Induction  apparatus,  closed  core,  23,  34 
Induction  apparatus,  open  core,  23 
Induction,  electro-magnetic,    II 
Induction,  electro-static,  3 
Induction,  magnetic,  3 


Induction,  magnetic  lines  of,   II 
Induction,  mutual,  12 
Induction,  self,  13 
Induction,  variable,  43 
Induced  current,  12,  23 

production  of,  12 
Ion,  2,  10 

lonto  quantimeter,   104 
Ionization  by  cathode  rays,  76 
Ionization  meter,  105 
Ionization  by  x-rays,  79 
Ionization.  2 
Indirect  radiation.  86 
Installations,  standard,  19 
Insulators,  3 
Insulation,  3 
Intensification,  212 
Intensification  screens.   137,   138 

uses  of,  138 
Intensification  of  plate,  212 
Instruments,  measuring.  20,  21 
Interrupter,  26 

Interrupter,  di-electric  used,  28 
Interrupter,  electrolytic,  29 

advantages  and  disadvantages  of,  30 
Interrupters,  mechanical,  26 
Interrupters,  motor  mercury,  69 
Interrupters,  mercury.  27,  28 
Interrupters.  Wehnelt.  29 
Interrupters,  method  of  action,  29 
Interrupters,  single  point,  29 
Interrupters,  three  point,  30 
Interrupters,  for  alternating  current,  33 
Interrupterless  apparatus,  34 
Interrupterless  apparatus,  wiring   diagram,  40 
Interrupterless  machine,  36-40 
Inverse  current,  91 


Jackson  tube.  62 

Jaw.  radiography  of,  intraoral.  155-160 

Jaw.  radiography  of,  extraoral.  160-162 

Jet  type  mercury  interrupter.  28 

Johnson,  114.  130 

Jordan.  69 


K 

Kenstron,  91 

Kidney,  radiography  of,  194 

Kienbock  scale,  105 

Kilovolt,  4 

Kilovoltmeter.  94 

Kilowatt.  6 

Kimoroentgenography.   135.  136 

Knee,   173.  174 

Knee,  radiography  of,   173 

Knipping,  77 


240 


INDEX 


Laboraton',  x-raj-.  217 

Lane,  77 

Lead  glass  protection,   114 

Lead  glass  tubes,  66 

Leakage,  high  tension,  123 

Leg,  175 

Leg,  radiograph}'  of,  174 

Lenard  tube,  57,  61 

Levelling  apparatus  for  head  radiography,  150 

Lillienfeld  circuit,  72 

Lillienfeld  tube.  72,  -^ 

Lindeman  x-ra}'  tubes,  66 

Loading  of  plate,  137 

Low  tension  voltages,  4 

Lumbar  spine,  167 

Lumbar  spine,  radiography  of,  167 

Lumbo-sacral  spine,  radiography  of,   168 

Luminous  effects  of  electricit}-,  10 

Lungs,  radiography  of,  185-187 

M 

Machine  operating  room,  233 
Magnetic  attraction,  10 
Magnetic  circuit,  II 
Magnetic  field,  11 

external,  11 

closed.  II 
Magnetic  force,  lines  of,  II 

laws  of,  II 
Magnetic  flux.  11 

cutting  of,  II 
Magnetic  leakage,  25 
Magnetic  poles,  10 
Magnetic  ring,  II 
Magnetic  spectrum.  75 
Magnets,  artificial,  11 

by  induction,  11 

kinds  of,  II 

natural,  II 

rectangular,  11 
Magnet,  temporary  inductive  action  of.  13 
Management  of  X-raj-  laboratory-,  219 
Mastoid  process,  radiography  of,   150 
^laxillary  sinuses,  radiography  of.  151 
Maximum  potential   measurement  by   equivalent   of 

spark  gap,  94 
^Maximum  potential  measurement  by   static   electro- 
meter, 95 
Maximum  potential  measurement  by  voltmeter,  93 
Maxillae  and  teeth.  155-162 
Measurement  of  wave  length.  102 
Measurement  of  x-ra3-s,  93 
Mercury  vapor  lamp  rectifier,  11 
Metacarpal  phalanges,  radiography  of,  184 
Metal  tube,  73 
Metatarsus,  radiograph}'  of,  177 


Meters,  Bauer,  96 

Benoist,  97 

Christen,  98 

Ionization,  105 

Semi-reducing,  99 
Methods,   serial  exposure,   131 
^Methods,  radiographic.  131 
Methods  of  X-ray  examination,  iii 
Metol.  208 

Milliamperemeter,  5,  124 
Milliampere  coil  outfit,  31 
Milliampere  method  of  testing,  125,  126.  219 
Alilliamperemeter   for  measuring  x-rays,   5,   124 
Mirror  stereoscope,  216 
Mobile  outfit  for  x-ray  work,  49,  55 
Molecular  pump,  60 
Moore,  56 
Morgan,  56 
^losele}'.  jy 
Motors,  16,  36 

Motors,  alternating  curve.    15 
!Motor  jprushes,  15 
Motor  car  —  x-ray  equipped,  55 
Alotors,  interrupterless  apparatus,  36 
Motors,  speed  of,  15 
Motors,  synchronous,  12,  15 
^Multiple  exposures  on  a  single  plate,  135 
Multiple  spark  gap,  90,  91 
Mutual  induction,  12 


N 


X'ickel  in  interrupters, 
X^on-conductors,  3 


30 


Object,  recording  surface  relationship,  142 

Object,  central  ray  relationship,  144 

Oblique  views,  141 

Occiput,  radiography  of,  150 

Ohm.  4 

Ohm's  law.  5 

Ohmic  resistance,  42 

Oil-cooled  tube,  64 

Open  core  transformer,  23,  24 

Optic  foramen,  radiography  of,  153 

Orthodiascopy,  basis  of  method,  118 

Orthofluoroscopy,  basis  of  method,  118 

Orthofluoroscopic  apparatus,  119.  120 

Oscillogram,  of  a  transformer  discharge.  46 

Oscillogram  of  a  coil  discharge,  46 

Oscilloscope,  91.  92 

Oxvgen  ions,  10 


Palpation  fluoroscope,  117 
Palpation  spoons,  116.  118 


INDEX 


241 


Paladium  regulator,  65 

Paramido-phenol,  207 

Parallel  rays,  118 

Parts  of  coil,  induction,  23,  24 

Parts,  thickness  of.  198 

Pelvis,  169 

Pelvis,  radiography  of,   169 

Penetration,  x-rays,  79 

Penetrometer,  comparative  values,  99 

Penetrometer,  Hirsch,  99 

Permanent  magnet,  inductive  action  of,  12 

Perpendicular  ray,  118 

Petrous  bone,  radiography  of,  154 

Phalanges,  radiography  of,   177 

Photograph  of  activated  Coolidge  tube,  83 

Photographic  dark  room.  207 

Photographic  methods.  106 

Photographic  plate,  i37 

Photography  of  x-rays.  81,  85 

Phosphorescence,  78 

Planning  x-ray  laboratory,  222 

Planning  small  x-ray  laboratory,  223 

Plate  development,  207 

Plate  examination,  213 

Plate  sensitiveness,  199 

Plate,  silver  bromide,  137 

Plate,  recording,  213 

Platinum  in  interrupter,  29 

Platinum  in  x-ray  tube  construction,  62 

Plucker,  56 

Pole  changes,  coil  outfit,  32 

Polygram,  134.  I3S 

Portable  apparatus,  49-5S 

Portable  coils,  49 

Portable  power  plant,  U,  S.  Army,  56 

Portable  unit,  U.  S.  Army,  50 

Positions  and  postures,   139 

Position  of  patient  in  fluoroscopy,  il" 

Position  of  tube,  142 

Positions,  standard,  I47-I94 

Postures  and  positions,  139 

Postures,  140 

Postures   for  teeth  examination,   155 

Potential.  4 

Potential  difference,  4 

Potential  measurement  by   relative   absorption,   96 

Potter's   diaphram,   91 

Power  factor,  6 

Power  plant,  portable,  50 

Primary  circuit,  23 

Primary  current,  interruption,  25 

Primary  and   secondary  rays,  89 

Primary  switch,  coil  outfit,  32 

Primary  winding,  23,  24 

Prism,  steresocope.  215 

Production  of  electro-magnetic  induction,  11 

Production  of  x-rays,  80,86 


Protection  of  workers  in  x-ray  laboratory,  226 
Protection  against  high  tension,  229 
Protection  during  fluoroscopy,  116 
Pulsating  current,   18 


Qualimeter,  Bauer,  95,  96 

Quality  of  ray,  method  of  measurement,  93 

Quantitative  measurement,   10,   104 


Radiator  tube,  64 

Radiation,  86 

Radiographic  department,  Bellevue,  Diagram  of,  224 

Radiographic  examination,  preparation    for,    121-131 

Radiographic,  examination,  General  131 

Radiographic  table,  122 

Radiographic  methods,  131 

Radiography,  121 

Radiological  axioms,  143,  I44 

Radiometer  absorption  table,  loi 

Radiometer,  Hampson-Holzknecht,  117 

Ray,  2 

Rays,  beta,  2 

Rays,  cathode,  2 

Ray,  central  or  vertical,  119 

Rays,  primary  and  secondary,  89 

characteristics,   of   89 
Ray  quality  as  effecting  exposure,   196 
Ray  quantity  as   effecting  exposure,   196 
Ray  quality  and  quantity  for  fluoroscopy,  1 16-195 
Records,  213 
Rectifier,  chemical,  19 
Rectifier,  high  tension,  37 
Rectifier,  low  tension,  15,  19 
Rectifier,  mercury  vapor  lamp,  19 
Rectifying  devices,  diagram  of,  19,  37 
Reducing  plate.  212 
Reels,  high  tension,  123 
Reflected  light,  213,  214 
Reflected  light,  examination  by,  214 
Regeneration   of   vacuum    of    x-ray    tubes,    methods 

used  for,  66 
Regulation   with   Coolidge   tube,   128 
Regulation  chamber,  65 
Regulator,  air  valve,  65 
Regulator  for  filament  current.  129 
Regulation  of  gas  tube,  125 
Relationship  of  object  to  recording  surface,    14^ 
Relationship  of  object  to  central  ray,  144 
Relationship  of  source  of  illumination  to  object,  143 
Reporting  x-ray  plates,  217 
Rheostat,  5 

Rheostat,  coil  interrupter,  31 
Rheostatic  control,   interrupterless   apparatus,   42 
Rheostatic  resistance,  42 


242 


INDEX 


Reluctance,  ii 

Resistance,  3,  4 

Resistance  unit,  5 

Rib,  radiography  of,   170 

Rib-sternum,  170 

Roentgenograph,  basis  of,  yy 

Roentgen's  discovery,  58 

Rooms,  equipment  of  x-ray  laboratory,  229-233 

Rotary   converter,   19 

Rotating  plate  changing  stand,  136 

Routine  of  x-ray  laboratory,  220 


Sacrum,  168 

Salivary  concretion,  arrangement  for,  151 

Salts,  fluorescent,  78 

Scapula,  radiography  of,  178 

Schwartz  quantitative  method,  194 

Screen  cleaning  of,   138 

Screen,  Dessani,   115 

Screen,  fluoroscopic,  114 

Screen,  intensifying,  138 

Secondary  cells,  8 

Secondary  radiation,  89 

Secondary  winding,  23,  24 

Section  of  x-ray  films,  210 

Self  induction,  13 

Sella-turcica,   radiography   of,   152 

Semi-conductors,  3 

Semi-reducing  meter,  99 

Semi-valency  meter,  lOO,  loi 

Sensitiveness  of  the  plate,  199 

Sensitization  of  the  eye,  116 

Separation  of  charges  by  generators,  4 

Serial  exposures,  135 

Serial  exposure  method,  133 

Series  connections,  8 

Shoulder,  179,  180 

Shoulder,   radiography   of,    179,    180 

Silver  bromide  plate,  137 

Skull,  radiography  of,  150 

Slip  rings,  15 

Solenoid,  12 

Solutions,  developing,  208 

Spark  gaps,  90,  91 

Spark  gap,  kilovolt  relationship,  94 

Spark  gap  measurement,  95 

Spark  gap  voltage,  95 

Sparking  potential,  93 

Spark  meter  for  Coolidge  tube  testing,  129 

Speed  of  plate,  198,  199 

Sphenoidal   sinuses,   radiography  of,   152,   153 

Spine,  163,  164.  165 

Spine,  radiological  examination  of,  164,  165 

Spine,  cervical,  164 

Spine,  dorsal,  165,  166 

Spine,  lumbar,  167 


Sputtering,  84 

Static  discharge,  123 

Static  electrometer,  96 

Standard  positions,  147-194 

Step-down  transformer,  69 

Stereo-fiuoroscope,   120 

Stereography,  131 

Stereoscopic  fluoroscopy,  120 

Stereoscopic  plates,  viewing  of,  215,  216 

Stereoscopy,  119 

Stereo-tubes,  64 

Sternum-ribs,   170 

Sternum,  radiography  of,  170 

Storage  batteries,  89 

care  of,  9 

charging  of,  8,  9 

connections  of,  9 

discharging  of,  9 

Edison,  9 

for  Coolidge  tube,  68,  69 
Switch,  high  tension,  123 
Switchboard,  coil  outfit,  31,  32 
Symphany,  216 


Tables,  exposure,  200-206 

Table,  x-ray,  U.  S.  Army,  52 

Table  and  tube  stand,  122 

Tank  development,  209 

Target,  Coolidge  tube  photograph  of,  86 

Target,  Coolidge  tube  emission  of  X-rays,  86 

Target,  x-ray  tube,  62,  d^i 

Tarsus,  radiography  of,  177 

Teeth,  155-160 

Teeth,  extraoral,  radiography,  161,  162 

Teeth,  radiography,  lower  jaw,  158 

Teeth,  radiography,  upper  jaw,   159 

Teeth,  radiography  of  horizontal  films,   160 

Teleographic  apparatus,   132 

Teleroentgenography,  134 

Temporary  magnet,  12 

Tension,  4 

Test,  focal  point,  7 

Testing  with  Coolidge  tube,  127 

Testing  gas  tube,  124 

Testing,  milliamjiere  method,  126 

Thermic  effects  of  electricity,  10 

Thickness  of  part,  198 

Thigh,  172 

Thigh,  radiography  of,  172 

Three  wire  system,  19 

Timing  of  exposure,  197 

Time  switch,  197 

Tintometer,  107 

Toes,  177 

Toes,  radiography  of,  177 

Torque,  15 


INDEX 


243 


Tracing  of  fluoroscopic  image,  115 

Tract,  urinary,  192,  193 

Transformation,  ratio  of,  42 

Transformer  action,  34 

Transformer  charts,  128 

Transformer,  closed  core,  34,  35,  36 

Transformer,  closed  core,  advantages  of,  43 

Transformer  construction,  23 

Transformer,  eiificiency  of,  35 

Transformer,  parts  of,  23 

Transformer,  principles  of,  23,  24,  25 

Transformer,  principle  of  induction,  14 

Transformer,  secondary  closed  circuit,  35 

Transformer,  secondary  open  circuit,  35 

Transformer,  step-down,  51 

Transformer,  step-up,  51 

Tube  centering  device,   iig 

Tube,  Crookes,  57,  60 

Tube  box  fluoroscope,  113 

Tube  Lenard,  57 

Tube  plate  distance,  ig6 

Tube  position,  141 

Tube  position,  teeth  examination,  15S 

Tube  position  in  reference  to  part,  142 

Tube  position  to  central  ray  relationship,  144 

Tube  stands,  121,  122,  230 

Tube,  table,  122 

Tube  test,  124,  126 

Tungstate  of  calcium  fluorescence,  78 

Tungsten  target,  63 

U 

Uranium  glass,  57,  66 

Uranium  intensifier,  212 

Urinary  tract,  192,  193 

Urinary  tract,  radiography  of,  192,  193,  194 

V 

Vacuum,  increase  by  usage,  82 

Vacuum  regulation,  65 

Valve  tubes,   19.  91 

Variable  induction.  43 

Variable  induction  control,  42 

Variable  spark  gap,   124,   128 

Velocity  by  electro-motive  force,  81 

Velocity  changes  in  cathode  stream,  80 

Ventro-dorsal,  first  oblique  140 

Ventro-dorsal,  second  oblique,  140 

Vertical  ray,  119 

Views,  centric  and  eccentric,  141 

Viewing  of  stereoscopic  plates,  216 

Volt,  4 

Volt,  kilo,  4 

Voltage,  primary,  42 

Voltage,  secondary,  42 

Voltage,  regulation  of,  42 


iVoltaic  battery,  7 

requisites  of,  8 
Voltaic  cells,  6 

high  internal  resistance  of,  8 

low  internal  resistance  of,  8 

parallel  connection  of,  8 

resistance  of,  7 

series  connection  of,  8 
Voltaic  element,  characteristics  of,  7 
Voltmeter,  20,  21 
Volt  or  spark  meter,  129 

W 

Wall  folding  table,  122 

Walter-Benoist  meters,  97 

Water  penetrometer,  97 

Water-cooled  tube.  64 

Watt,  6 

Wave  length  measurement,   102 

Wehnelt  meter,  97 

Wehnelt  interrupter,  29 

Wehnelt  interrupter,  cold  water  jacket,  30 

Wheatstone  stereoscope.  216 

Winding,  primary,  24 

Winding,   secondary,  24 

Wiring  diagram,  A.  C.  Machine,  39 

Wiring  diagram,  D.  C.  Machine,  38 

Wiring,  high  tension,   123 

Wiring  table,  18 

Workers  protection,  226,  227 

Wrist  and  hand,  radiography  of,  183 


X-rays,  2 

X-ray  absorption.  78 

X-rays,  absorption  by  substances,   78 

X-ray,  action  on  bromide  of  silver  plate,  77 

X-ray,  biological  effects  of,  79 

X-ray,  central  ray,  118 

X-ray,  chemical  efifects  of,  79 

X-ray,  characteristics  of,  85,  90 

X-ray,  discovery  of,  55-59 

X-ray  department,  218 

accommodations,  222 

director.  219 

equipment  of,  218,  229 

equipment  of  rooms.  230-233 

maintenance  of,  218 

management  of.  219 

plan  of  small  laboratory,  223,  224 

reports  of,  221 
X-ray  distribution  on  hemispheres,  80 
X-ray  tubes,  exhaustion  of.  60 
X-ray  fluorescence,  78,   104 
X-ray  ionization,  79 
X-ray  laboratory,  217,  218 


244 


INDEX 


X-ray  measurement,  93 

by  chemical  reaction,  107 

by  color  reaction,  106 

by  complete  absorption,  97 

by  half  absorption,  97 

photographic,  105 

by  wave  length,  10,  yy,  102 
X-rays,  nature  of,  y- 
X-ray,  penetrating  power  of,  78 
X-ray,  penetration  by,  78 
X-ray,  penetration  of  human  body,  78 
X-ray,  photographic  plate,   137 
X-ray,  production,  80,  81 
X-ray  production  through  cathode  rays,  "jd 
X-ray,  properties  of,  TJ 
X-ray,  quantitative  measurement,  103,   104 
X-ray,  source  of,  2 
X-ray,  spectrum,    105 
X-ray  refraction,  105 
X-ray  tubes,  61,  62 

accessory  anode  of,  62 

activated,  81-83 

activated,  photographs  of,  81-83 

anticathode  of,  62 

cathode  of,  62,  75,  76 

charging  of  walls  of,  83 

changes  in  vacuum,  68 


Coolidge,  68 

battery  for,  68 
cathode  of,  68 
characteristics  of,  68-70 
method  of  operating,  70,  71 
changes  in  shape  and  size,  66 
requisites  of  target  of  tube,  63 
regulation  of,  126,  127 

diaphragms  of.  86 

discolorization  of,  83 

focal  point,  85 

forms  of,  70 

low  vacumm  of,  60,  80 

lowering  of  vacuum  of,  60,  65,  66 

maintenance  of  sharp  focus,  85 

methods  of  testing,  124 

modern,  61 

potential  difference  in,  81 

varieties  of,  78 
X-ray  unit,  portable,  French,  53 
X-ray  wave  lengths,  J"/ 


Zinc  blend  fluorescence,  78 

Zinc  element,  7 

Zinc  oxide  fluorescence,  78 


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